1.
What is the major difference between 10g and 11g RAC?
Well,
there is not much difference between 10g and 11gR (1) RAC.
But
there is a significant difference in 11gR2.
Prior
to 11gR1(10g) RAC, the following were managed by Oracle CRS
- Databases
- Instances
- Applications
- Node Monitoring
- Event Services
- High
Availability
From
11gR2(onwards) its completed HA stack managing and providing the following
resources as like the other cluster software like VCS etc.
- Databases
- Instances
- Applications
- Cluster
Management
- Node
Management
- Event
Services
- High Availability
- Network
Management (provides DNS/GNS/MDNSD services on behalf of other traditional
services) and SCAN – Single Access Client Naming method, HAIP
- Storage
Management (with help of ASM and other new ACFS filesystem)
- Time
synchronization (rather depending upon traditional NTP)
- Removed
OS dependent hang checker etc, manages with own additional monitor process
2.
What are Oracle Cluster Components?
Cluster
Interconnect (HAIP)
Shared
Storage (OCR/Voting Disk)
Clusterware
software
3.
What are Oracle RAC Components?
VIP,
Node apps etc.
4.
What are Oracle Kernel Components (nothing but how does Oracle RAC database
differs than Normal single instance database in terms of Binaries and process)
Basically
Oracle kernel need to switched on with RAC On option when you convert to RAC,
that is the difference as it facilitates few RAC bg process like
LMON,LCK,LMD,LMS etc.
To turn on RAC
# link the oracle libraries
$ cd $ORACLE_HOME/rdbms/lib
$ make -f ins_rdbms.mk rac_on
# rebuild oracle
$ cd $ORACLE_HOME/bin
$ relink oracle
# link the oracle libraries
$ cd $ORACLE_HOME/rdbms/lib
$ make -f ins_rdbms.mk rac_on
# rebuild oracle
$ cd $ORACLE_HOME/bin
$ relink oracle
Oracle
RAC is composed of two or more database instances. They are composed of Memory
structures and background processes same as the single instance database.Oracle
RAC instances use two processes GES(Global Enqueue Service), GCS(Global Cache
Service) that enable cache fusion.Oracle RAC instances are composed of
following background processes:
ACMS—Atomic
Controlfile to Memory Service (ACMS)
GTX0-j—Global Transaction Process
LMON—Global Enqueue Service Monitor
LMD—Global Enqueue Service Daemon
LMS—Global Cache Service Process
LCK0—Instance Enqueue Process
RMSn—Oracle RAC Management Processes (RMSn)
RSMN—Remote Slave Monitor
GTX0-j—Global Transaction Process
LMON—Global Enqueue Service Monitor
LMD—Global Enqueue Service Daemon
LMS—Global Cache Service Process
LCK0—Instance Enqueue Process
RMSn—Oracle RAC Management Processes (RMSn)
RSMN—Remote Slave Monitor
5.
What is Clusterware?
Software
that provides various interfaces and services for a cluster. Typically, this
includes capabilities that:
- Allow
the cluster to be managed as a whole
- Protect
the integrity of the cluster
- Maintain
a registry of resources across the cluster
- Deal
with changes to the cluster
- Provide
a common view of resources
6.
What are the background process that exists in 11gr2 and functionality?
|
Process
Name
|
Functionality
|
|
crsd
|
•The
CRS daemon (crsd) manages cluster resources based on configuration
information that is stored in Oracle Cluster Registry (OCR) for each
resource. This includes start, stop, monitor, and failover operations. The
crsd process generates events when the status of a resource changes.
|
|
cssd
|
•Cluster
Synchronization Service (CSS): Manages the cluster configuration by
controlling which nodes are members of the cluster and by notifying members
when a node joins or leaves the cluster. If you are using certified
third-party clusterware, then CSS processes interfaces with your clusterware
to manage node membership information. CSS has three separate processes: the
CSS daemon (ocssd), the CSS Agent (cssdagent), and the CSS Monitor
(cssdmonitor). The cssdagent process monitors the cluster and provides
input/output fencing. This service formerly was provided by Oracle Process
Monitor daemon (oprocd), also known as OraFenceService on Windows. A
cssdagent failure results in Oracle Clusterware restarting the node.
|
|
diskmon
|
•Disk
Monitor daemon (diskmon): Monitors and performs input/output fencing for
Oracle Exadata Storage Server. As Exadata storage can be added to any Oracle
RAC node at any point in time, the diskmon daemon is always started when
ocssd is started.
|
|
evmd
|
•Event
Manager (EVM): Is a background process that publishes Oracle Clusterware
events
|
|
mdnsd
|
•Multicast
domain name service (mDNS): Allows DNS requests. The mDNS process is a
background process on Linux and UNIX, and a service on Windows.
|
|
gnsd
|
•Oracle
Grid Naming Service (GNS): Is a gateway between the cluster mDNS and external
DNS servers. The GNS process performs name resolution within the cluster.
|
|
ons
|
•Oracle
Notification Service (ONS): Is a publish-and-subscribe service for
communicating Fast Application Notification (FAN) events
|
|
oraagent
|
•oraagent:
Extends clusterware to support Oracle-specific requirements and complex
resources. It runs server callout scripts when FAN events occur. This process
was known as RACG in Oracle Clusterware 11g Release 1 (11.1).
|
|
orarootagent
|
•Oracle
root agent (orarootagent): Is a specialized oraagent process that helps CRSD
manage resources owned by root, such as the network, and the Grid virtual IP
address
|
|
oclskd
|
•Cluster
kill daemon (oclskd): Handles instance/node evictions requests that have been
escalated to CSS
|
|
gipcd
|
•Grid
IPC daemon (gipcd): Is a helper daemon for the communications infrastructure
|
|
ctssd
|
•Cluster
time synchronisation daemon(ctssd) to manage the time syncrhonization between
nodes, rather depending on NTP
|
7.
Under which user or owner the process will start?
|
Component
|
Name
of the Process
|
Owner
|
|
Oracle
High Availability Service
|
ohasd
|
init,
root
|
|
Cluster
Ready Service (CRS)
|
Cluster
Ready Services
|
root
|
|
Cluster
Synchronization Service (CSS)
|
ocssd,cssd
monitor, cssdagent
|
grid
owner
|
|
Event
Manager (EVM)
|
evmd,
evmlogger
|
grid
owner
|
|
Cluster
Time Synchronization Service (CTSS)
|
octssd
|
root
|
|
Oracle
Notification Service (ONS)
|
ons,
eons
|
grid
owner
|
|
Oracle
Agent
|
oragent
|
grid
owner
|
|
Oracle
Root Agent
|
orarootagent
|
root
|
|
Grid
Naming Service (GNS)
|
gnsd
|
root
|
|
Grid
Plug and Play (GPnP)
|
gpnpd
|
grid
owner
|
|
Multicast
domain name service (mDNS)
|
mdnsd
|
grid
owner
|
8.
What is startup sequence in Oracle 11g RAC? 11g RAC startup sequence?
9.
As you said Voting & OCR Disk resides in ASM Diskgroups, but as per startup
sequence OCSSD starts first before than ASM, how is it possible?
How
does OCSSD starts if voting disk & OCR resides in ASM Diskgroups?
You
might wonder how CSSD, which is required to start the clustered ASM instance,
can be started if voting disks are stored in ASM? This sounds like a
chicken-and-egg problem: without access to the voting disks there is no CSS,
hence the node cannot join the cluster. But without being part of the cluster,
CSSD cannot start the ASM instance. To solve this problem the ASM disk headers
have new metadata in 11.2: you can use kfed to read the header of an ASM disk
containing a voting disk. The kfdhdb.vfstart and kfdhdb.vfend fields tell CSS
where to find the voting file. This does not require the ASM instance to be up.
Once the voting disks are located, CSS can access them and joins the cluster.
10.
How does SCAN works?
1.Client
Connected through SCAN name of the cluster (remember all three IP addresses
round robin resolves to same Host name (SCAN Name), here in this case our scan
name is cluster01-scan.cluster01.example.com
2.The
request reaches to DNS server in
your corp and then resolves to one of the node out of three. a. If GNS
(Grid Naming service or domain is configured) that is a subdomain configured
in the DNS entry for to resolve cluster address the request will be
handover to GNS (gnsd)
3.Here
in our case assume there is no GNS, now the with the help of SCAN listeners
where end points are configured to database listener.
4.Database
Listeners listen the request and then process further.
5.In
case of node addition, Listener 4, client need not to know or need not change
any thing from their tns entry (address of 4thnode/instance) as they
just using scan IP.
6.Same
case even in the node deletion.
11.
What is GNS?
Grid
Naming service is alternative service to DNS , which will act as a sub domain
in your DNS but managed by Oracle, with GNS the connection is routed to the
cluster IP and manages internally.
12.
What is GPNP?
Grid
Plug and Play along with GNS provide dynamic
In
previous releases, adding or removing servers in a cluster required extensive
manual preparation.
In Oracle Database 11g Release
2, GPnP allows each node to perform the following tasks dynamically:
- Negotiating appropriate network identities for itself
- Acquiring additional information from a configuration
profile
- Configuring or reconfiguring itself using profile
data, making host names and addresses resolvable on the network
For
example a domain should contain
- –Cluster
name: cluster01
- –Network
domain: example.com
- –GPnP
domain: cluster01.example.com
To
add a node, simply connect the server to the cluster and allow the cluster to
configure the node.
To
make it happen, Oracle uses the profile located in
$GI_HOME/gpnp/profiles/peer/profile.xml which contains the cluster resources,
for example disk locations of ASM. etc.
So
this profile will be read local or from the remote machine when plugged into
cluster and dynamically added to cluster.
13.
What are the file types that ASM support and keep in disk groups?
|
Control
files
|
Flashback
logs
|
Data
Pump dump sets
|
|
Data
files
|
DB
SPFILE
|
Data
Guard configuration
|
|
Temporary
data files
|
RMAN
backup sets
|
Change
tracking bitmaps
|
|
Online
redo logs
|
RMAN
data file copies
|
OCR
files
|
|
Archive
logs
|
Transport
data files
|
ASM
SPFILE
|
14.
List Key benefits of ASM?
- Stripes
files rather than logical volumes
- Provides
redundancy on a file basis
- Enables
online disk reconfiguration and dynamic rebalancing
- Reduces
the time significantly to resynchronize a transient failure by tracking
changes while disk is offline
- Provides
adjustable rebalancing speed
- Is
cluster-aware
- Supports
reading from mirrored copy instead of primary copy for extended clusters
- Is
automatically installed as part of the Grid Infrastructure
15.
List key benefits of Oracle Grid Infrastructure?
16.
List some of the background process that used in ASM?
|
Process
|
Description
|
||
|
RBAL
|
Opens
all device files as part of discovery and coordinates the rebalance activity
|
||
|
ARBn
|
One
or more slave processes that do the rebalance activity
|
||
|
GMON
|
Responsible
for managing the disk-level activities such as drop or offline and advancing
the ASM disk group compatibility
|
||
|
MARK
|
Marks
ASM allocation units as stale when needed
|
||
|
Onnn
|
One
or more ASM slave processes forming a pool of connections to the ASM instance
for exchanging messages
|
||
|
PZ9n
|
One
or more parallel slave processes used in fetching data on clustered ASM
installation from GV$ views
|
||
13.
What is node listener?
In 11gr2 the listeners will run from Grid Infrastructure
software home
- The
node listener is a process that helps establish network connections from
ASM clients to the ASM instance.
- Runs
by default from the Grid $ORACLE_HOME/bin directory
- Listens
on port 1521 by default
- Is
the same as a database instance listener
- Is
capable of listening for all database instances on the same machine in
addition to the ASM instance
- Can
run concurrently with separate database listeners or be replaced by a
separate database listener
- Is
named tnslsnr on the Linux platform
15.
What is SCAN listener?
A
scan listener is something that additional to node listener which listens the
incoming db connection requests from the client which got through the scan IP,
it got end points configured to node listener where it routes the db connection
requests to particular node listener.
16.
What is the difference between CRSCTL and SRVCTL?
crsctl
manages clusterware-related operations:
- Starting
and stopping Oracle Clusterware
- Enabling
and disabling Oracle Clusterware daemons
- Registering
cluster resources
srvctl
manages Oracle resource–related operations:
- Starting
and stopping database instances and services
- Also
from 11gR2 manages the cluster resources like network,vip,disks etc
17.
How to control Oracle Clusterware?
To
start or stop Oracle Clusterware on a specific node:
# crsctl stop crs
# crsctl start crs
To
enable or disable Oracle Clusterware on a specific node:
# crsctl enable crs
# crsctl disable crs
19.
How to check the cluster (all nodes) status?
To
check the viability of Cluster Synchronization Services (CSS) across nodes:
$ crsctl check cluster
CRS-4537: Cluster Ready Services is online
CRS-4529: Cluster Synchronization Services is online
CRS-4533: Event Manager is online
20.
How to check the cluster (one node) status?
$ crsctl check crs
CRS-4537: Cluster Ready Services is online
CRS-4529: Cluster Synchronization Services is online
CRS-4533: Event Manager is online
21.
How to find Voting Disk location?
•To
determine the location of the voting disk:
# crsctl query css votedisk
## STATE File Universal Id File Name Disk group
– —– —————– ———- ———-
1. ONLINE 8c2e45d734c64f8abf9f136990f3daf8 (ASMDISK01) [DATA]
2. ONLINE 99bc153df3b84fb4bf071d916089fd4a (ASMDISK02) [DATA]
3. ONLINE 0b090b6b19154fc1bf5913bc70340921 (ASMDISK03) [DATA]
Located 3 voting disk(s).
22.
How to find Location of OCR?
- cat
/etc/oracle/ocr.loc
ocrconfig_loc=+DATA
local_only=FALSE
- #OCRCHECK
(also about OCR integrity)
23.
List some background process that used in ASM Instances?
|
Process
|
Description
|
|
RBAL
|
Opens
all device files as part of discovery and coordinates the rebalance activity
|
|
ARBn
|
One
or more slave processes that do the rebalance activity
|
|
GMON
|
Responsible
for managing the disk-level activities such as drop or offline and advancing
the ASM disk group compatibility
|
|
MARK
|
Marks
ASM allocation units as stale when needed
|
|
Onnn
|
One
or more ASM slave processes forming a pool of connections to the ASM instance
for exchanging messages
|
|
PZ9n
|
One
or more parallel slave processes used in fetching data on clustered ASM
installation from GV$ views
|
24.
What are types of ASM Mirroring?
|
Disk
Group Type
|
Supported
MirroringLevels
|
Default
Mirroring Level
|
|
External
redundancy
|
Unprotected
(None)
|
Unprotected
(None)
|
|
Normal
redundancy
|
Two-wayThree-wayUnprotected
(None)
|
Two-way
|
|
High
redundancy
|
Three-way
|
Three-way
|
25.
What is ASM Striping?
ASM
can use variable size data extents to support larger files, reduce memory
requirements, and improve performance.
Each
data extent resides on an individual disk.
Data
extents consist of one or more allocation units.
The
data extent size is:
- Equal
to AU for the first 20,000 extents (0–19999)
- Equal
to 4 × AU for the next 20,000 extents (20000–39999)
- Equal
to 16 × AU for extents above 40,000
ASM
stripes files using extents with a coarse method for load balancing or a fine
method to reduce latency.
- Coarse-grained
striping is always equal to the effective AU size.
- Fine-grained
striping is always equal to 128 KB.
26.
How many ASM Diskgroups can be created under one ASM Instance?
ASM
imposes the following limits:
- 63
disk groups in a storage system
- 10,000
ASM disks in a storage system
- Two-terabyte
maximum storage for each ASM disk (non-Exadata)
- Four-petabyte
maximum storage for each ASM disk (Exadata)
- 40-exabyte
maximum storage for each storage system
- 1 million files for
each disk group
- ASM
file size limits (database limit is 128 TB):
1.External
redundancy maximum file size is 140 PB.
2.Normal
redundancy maximum file size is 42 PB.
3.High
redundancy maximum file size is 15 PB.
27.
How to find the cluster network settings?
To
determine the list of interfaces available to the cluster:
$ oifcfg iflist –p -n
To
determine the public and private interfaces that have been configured:
$ oifcfg getif
eth0 192.0.2.0 global public
eth1 192.168.1.0 global cluster_interconnect
To
determine the Virtual IP (VIP) host name, VIP address, VIP subnet mask, and VIP
interface name:
$ srvctl config nodeapps -a
VIP exists.:host01
VIP exists.: /192.0.2.247/192.0.2.247/255.255.255.0/eth0
…
28.
How to change Public or VIP Address in RAC Cluster?
29.
How to change Cluster interconnect in RAC?
On
a single node in the cluster, add the new global interface specification:
$ oifcfg setif -global eth2/192.0.2.0:cluster_interconnect
Verify
the changes with oifcfg getif and then stop Clusterware on all nodes by running
the following command as root on each node:
# oifcfg getif
# crsctl stop crs
Assign
the network address to the new network adapters on all nodes using ifconfig:
#ifconfig eth2 192.0.2.15 netmask 255.255.255.0
broadcast 192.0.2.255
Remove
the former adapter/subnet specification and restart Clusterware:
$ oifcfgdelif -global eth1/192.168.1.0
# crsctl start crs
30.
Managing or Modifying SCAN in Oracle RAC?
To
add a SCAN VIP resource:
$ srvctl add scan -n cluster01-scan
To
remove Clusterware resources from SCAN VIPs:
$ srvctl remove scan [-f]
To
add a SCAN listener resource:
$ srvctl add scan_listener
$ srvctl add scan_listener -p 1521
To
remove Clusterware resources from all SCAN listeners:
$ srvctl remove scan_listener [-f]
31.
How to check the node connectivity in Oracle Grid Infrastructure?
$ cluvfy comp nodecon -n all –verbose
32.
Can I stop all nodes in one command? Meaning that stopping whole cluster ?
In
10g its not possible, where in 11g it is possible
[root@pic1]# crsctl start cluster -all
[root@pic2]# crsctl stop cluster –all
[root@pic2]# crsctl stop cluster –all
33.
What is OLR? Which of the following statements regarding the Oracle Local
Registry (OLR) is true?
1.Each
cluster node has a local registry for node-specific resources.
2.The
OLR should be manually created after installing Grid Infrastructure on each
node in the cluster.
3.One
of its functions is to facilitate Clusterware startup in situations where the
ASM stores the OCR and voting disks.
4.You
can check the status of the OLR using ocrcheck.
34.
What is runfixup.sh script in Oracle Clusterware 11g release 2
installation
With
Oracle Clusterware 11g release 2, Oracle Universal Installer (OUI) detects when
the minimum requirements for an installation are not met, and creates shell
scripts, called fixup scripts, to finish incomplete system configuration steps.
If OUI detects an incomplete task, then it generates fixup scripts
(runfixup.sh). You can run the fixup script after you click the Fix and Check
Again Button.
The
Fixup script does the following:
If
necessary sets kernel parameters to values required for successful
installation, including:
- Shared
memory parameters.
- Open
file descriptor and UDP send/receive parameters.
Sets
permissions on the Oracle Inventory (central inventory) directory. Reconfigures
primary and secondary group memberships for the installation owner, if
necessary, for the Oracle Inventory directory and the operating system
privileges groups.
- Sets
shell limits if necessary to required values.
35.
How to stop whole cluster with single command
crsctl stop cluster (possible only from 11gr2), please note crsctl
commands becomes global now, if you do not specify node specifically the
command executed globally for example
crsctl stop crs (stops in all crs resource in all nodes)
crsctl stop crs –n <ndeoname) (stops only in specified node)
36.
CRS is not starting automatically after a node reboot, what you do to make it
happen?
crsctl
enable crs (as root)
to
disable
crsctl
disable crs (as root)
37.
What are server pools in 11gr2?
38.
What is policy managed databases in RAC?
39.
What is Load balancing & how does it work?
40.
Describe high level Steps to convert single instance to RAC?
41.
What is the difference between TAF and FAN & FCF? at what conditions you
use them?
1)
TAF with tnsnames
a feature of Oracle Net Services for OCI8 clients. TAF is transparent application failover which will move a session to a backup connection if the session fails. With Oracle 10g Release 2, you can define the TAF policy on the service using dbms_service package. It will only work with OCI clients. It will only move the session and if the parameter is set, it will failover the select statement. For insert, update or delete transactions, the application must be TAF aware and roll back the transaction. YES, you should enable FCF on your OCI client when you use TAF, it will make the failover faster.
Note: TAF will not work with JDBC thin.
2) FAN with tnsnames with aq notifications true
a feature of Oracle Net Services for OCI8 clients. TAF is transparent application failover which will move a session to a backup connection if the session fails. With Oracle 10g Release 2, you can define the TAF policy on the service using dbms_service package. It will only work with OCI clients. It will only move the session and if the parameter is set, it will failover the select statement. For insert, update or delete transactions, the application must be TAF aware and roll back the transaction. YES, you should enable FCF on your OCI client when you use TAF, it will make the failover faster.
Note: TAF will not work with JDBC thin.
2) FAN with tnsnames with aq notifications true
FAN
is a feature of Oracle RAC which stands for Fast Application Notification. This
allows the database to notify the client of any change (Node up/down, instance
up/down, database up/down). For integrated clients, inflight transactions are
interrupted and an error message is returned. Inactive connections are
terminated.
FCF is the client feature for Oracle Clients that have integrated with FAN to provide fast failover for connections. Oracle JDBC Implicit Connection Cache, Oracle Data Provider for .NET (ODP.NET) and Oracle Call Interface are all integrated clients which provide the Fast Connection Failover feature.
3) FCF, along with FAN when using connection pools
FCF is a feature of Oracle clients that are integrated to receive FAN events and abort inflight transactions, clean up connections when a down event is received as well as create new connections when a up event is received. Tomcat or JBOSS can take advantage of FCF if the Oracle connection pool is used underneath. This can be either UCP (Universal Connection Pool for JAVA) or ICC (JDBC Implicit Connection Cache). UCP is recommended as ICC will be deprecated in a future release.
FCF is the client feature for Oracle Clients that have integrated with FAN to provide fast failover for connections. Oracle JDBC Implicit Connection Cache, Oracle Data Provider for .NET (ODP.NET) and Oracle Call Interface are all integrated clients which provide the Fast Connection Failover feature.
3) FCF, along with FAN when using connection pools
FCF is a feature of Oracle clients that are integrated to receive FAN events and abort inflight transactions, clean up connections when a down event is received as well as create new connections when a up event is received. Tomcat or JBOSS can take advantage of FCF if the Oracle connection pool is used underneath. This can be either UCP (Universal Connection Pool for JAVA) or ICC (JDBC Implicit Connection Cache). UCP is recommended as ICC will be deprecated in a future release.
4)
ONS, with clusterware either FAN/FCF
ONS
is part of the clusterware and is used to propagate messages both between nodes
and to application-tiers
ONS is the foundation for FAN upon which is built FCF.
RAC uses FAN to publish configuration changes and LBA events. Applications can react as those published events in two way :
- by using ONS api (you need to program it)
- by using FCF (automatic by using JDBC implicit connection cache on the application server)
you can also respond to FAN event by using server-side callout but this on the server side (as their name suggests it)
ONS is the foundation for FAN upon which is built FCF.
RAC uses FAN to publish configuration changes and LBA events. Applications can react as those published events in two way :
- by using ONS api (you need to program it)
- by using FCF (automatic by using JDBC implicit connection cache on the application server)
you can also respond to FAN event by using server-side callout but this on the server side (as their name suggests it)
Relationship
between FAN/FCF/ONS
ONS
–> FAN –> FCF
ONS -> send/receive messages on local and remote nodes.
FAN -> uses ONS to notify other processes about changes in configuration of service level
FCF -> uses FAN information working with conection pools JAVA and others.
ONS -> send/receive messages on local and remote nodes.
FAN -> uses ONS to notify other processes about changes in configuration of service level
FCF -> uses FAN information working with conection pools JAVA and others.
42.
Can you add voting disk online? Do you need voting disk backup?
Yes,
as per documentation, if you have multiple voting disk you can add online, but
if you have only one voting disk , by that cluster will be down as its lost you
just need to start crs in exclusive mode and add the votedisk using
crsctl
add votedisk <path>
43.
You have lost OCR disk, what is your next step?
The
cluster stack will be down due to the fact that cssd is unable to maintain the
integrity, this is true in 10g, From 11gR2 onwards, the crsd stack will be
down, the hasd still up and running. You can add the ocr back by restoring
the automatic backup or
import the manual backup,
44.
What happens when ocssd fails, what is node eviction? how does node eviction
happens? For all answer will be same.
45.
What is virtual IP and how does it works?
46.
Describe some rac wait events you experienced?
and
this table,
47.
Can you modify VIP address after your cluster installation?
Yes, read here
48.
How do you interpret AWR report in RAC instances, what sections in awr report
for rac instances are most important?
Read
here.
Update
12-May-2013, Some practical questions added here
1.
Viewing Contents in OCR/Voting disks
There are three possible
ways to view the OCR contents.
a.
OCRDUMP (or)
b.
crs_stat -p (or)
c. By using strings.
Voting disk contents are not persistent and are not required to view
the contents, because the voting disk contents will be overwritten. if still need to view, strings are used.
2.
Server pools – Read in my blog
3.
Verifying Cluster Interconnect
Cluster interconnects can
be verified by:
i.
oifcfg getif
ii. From AWR Report.
iii.
show parameter cluster_interconnect
iv.
srvctl config network
4.
Does scan IP required or we can disable it
SCAN IP can be
disabled if not required. However SCAN IP is mandatory during the RAC installation. Enabling/disabling SCAN IP is mostly used in oracle apps environment by the concurrent
manager (kind of job scheduler in oracle apps).
To disable the SCAN
IP,
i. Do not use SCAN IP at the
client end.
ii. Stop scan listener
srvctl stop scan_listener
iii. Stop scan
srvctl stop scan (this will stop the scan vip's)
iv. Disable scan and disable scan listener
srvctl disable scan
5.
Migrating to new Diskgroup scenarious
a. Case 1: Migrating disk group from one storage to other with same name
1. Consider the disk group is DATA,
2. Create new disks in DATA pointing
towards the new storage (EMC),
a) Partioning provisioning done by storage and they give you the
device name or mapper like /dev/mapper/asakljdlas
3. Add the new disk to diskgroup
DATA
a) Alter diskgroup data add
disk '/dev/mapper/asakljdlas'
3. drop the old disks from DATA with which rebalancing is done automatically.
If you want you can
the rebalance by alter system set asm_power_limit =12 for full throttle.
alter diskgroup data drop disk 'path
to hitachi storage'
Note: you can get the device name in v$asm_disk in path column.
4. Request SAN team to detach
the old Storage (HITACHI).
b. Case 2: Migrating disk group from one to another with different diskgroup name.
1) Create the Disk group with new name in the new storage.
2) Create the spfile in new diskgroup and change the parameter scope = spfile for control files etc.
3) Take a control file backup in format +newdiskgroup
4) Shutdown the db, startup nomount the database
5) restore the control file from backup (now the control will
restore to new diskgroup)
6) Take the RMAN backup as copy of all the databases with new format.
RMAN> backup
database as copy format '+newdiskgroup
name' ;
3) RMAN> Switch database to copy.
4) Verify dba_data_files,dba_temp_files, v$log that all files are pointing to new diskgroup name.
c. Case 3: Migrating disk group to new storage but no additional diskgroup given
1) Take the RMAN backup as copy of all the databases with new format and place it in the disk.
2) Prepare rename commands from v$log ,v$datafile etc (dynamic queries)
3) Take a backup of pfile and modify the following referring to new diskgroup name
.control_files
.db_create_file_dest
.db_create_online_log_dest_1
.db_create_online_log_dest_2
.db_recovery_file_des
4) stop the database
5) Unmount the diskgroup
asmcmd umount ORA_DATA
6) use asmcmd renamedg (11gr2 only) command to rename
to new diskgroup
renamedg phase=both dgname=ORA_DATA newdgname=NEW_DATA verbose=true
7) mount the diskgroup
asmcmd mount NEW_DATA
8) start the database in mount with new pfile taken backup in step 3
9) Run the rename file scripts generated at step2
9) Add the diskgroup to cluster the cluster (if using rac)
srvctl modify database -d orcl -p +NEW_FRA/orcl/spfileorcl.ora
srvctl modify database -d orcl -a "NEW_DATA"
srvctl config database -d orcl
srvctl start database -d orcl
10) Delete the old diskgroup from cluster
crsctl delete resource ora.ORA_DATA.dg
11) Open the database.
7.
Database rename in RAC, what could be the checklist for you?
a. Take the outputs of all
the services that are running on the databases.
b. set cluster_database=FALSE
c. Drop all the services
associated with the database.
d. Stop the database
e. Startup mount
f. Use nid to change the
DB Name.
Generic question, If using ASM the usual location for the datafile would
be +DATA/datafile/OLDDBNAME/system01.dbf'
Does NID changes this path too? to reflect the new db name?
Yes it will, by using proper directory structure it will create a links
to original directory structure. +DATA/datafile/NEWDBNAME/system01.dbf'
this has to be tested, We dont have test bed, but thanks to Anji who confirmed it will
g. Change the parameters
according to the new database name
h. Change the password file.
i. Stop the database.
j. Mount the database
k. Open database with Reset logs
l. Create spfile from pfile.
m. Add database to the
cluster.
n. Create the services that
are dropped in prior to rename.
o. Bounce the database.
8.How
to find the database in which particular service is attached to when you have a
large number of databases running in the server, you cannot check one by one
manually
Write
a shell script to read the database name from oratab and iterate the loop
taking inpt as DB name in srvctl to get the result.
#!/bin/ksh
ORACLE_HOME=
PATH=$ORACLE_HOME/bin:$PATH
LD_LIBRARY_PATH=${SAVE_LLP}:${ORACLE_HOME}/lib
export TNS_ADMIN ORACLE_HOME PATH LD_LIBRARY_PATH
for INSTANCE in `cat /etc/oratab|grep -v "^#"|cut -f1 -d: -s`
do
export ORACLE_SID=$INSTANCE
echo `srvctl status service -d $INSTANCE -s $1| grep -i "is running"`
done
#!/bin/ksh
ORACLE_HOME=
PATH=$ORACLE_HOME/bin:$PATH
LD_LIBRARY_PATH=${SAVE_LLP}:${ORACLE_HOME}/lib
export TNS_ADMIN ORACLE_HOME PATH LD_LIBRARY_PATH
for INSTANCE in `cat /etc/oratab|grep -v "^#"|cut -f1 -d: -s`
do
export ORACLE_SID=$INSTANCE
echo `srvctl status service -d $INSTANCE -s $1| grep -i "is running"`
done
9.
Difference between OHAS and CRS
OHAS is complete cluster stack which includes some kernel level tasks like managing network,time synchronization, disks etc, where the CRS has the ability to manage the resources like database,listeners,applications, etc With both of this Oracle provides the high availability
OHAS is complete cluster stack which includes some kernel level tasks like managing network,time synchronization, disks etc, where the CRS has the ability to manage the resources like database,listeners,applications, etc With both of this Oracle provides the high availability
Oracle RAC Interview Questions & Answers
1. Where are the
Clusterware files stored on a RAC environment?
The Clusterware is installed on each node (on an Oracle Home) and on the shared disks (the voting disks and the CSR file)
The Clusterware is installed on each node (on an Oracle Home) and on the shared disks (the voting disks and the CSR file)
2. Where are the
database software files stored on a RAC environment?
The base software is installed on each node of
the cluster and the
database storage on the shared disks.
database storage on the shared disks.
3. What kind of
storage we can use for the shared Clusterware files?
- OCFS (Release 1 or 2)
- raw devices
- third party cluster file system such as GPFS or Veritas
- OCFS (Release 1 or 2)
- raw devices
- third party cluster file system such as GPFS or Veritas
4. What kind of
storage we can use for the RAC database storage?
- OCFS (Release 1 or 2)
- ASM
- raw devices
- third party cluster file system such as GPFS or Veritas
- OCFS (Release 1 or 2)
- ASM
- raw devices
- third party cluster file system such as GPFS or Veritas
5. What is a CFS?
A cluster File System (CFS) is a file system that may be accessed (read and write) by all members in a cluster at the same time. This implies that all members of a cluster have the same view.
A cluster File System (CFS) is a file system that may be accessed (read and write) by all members in a cluster at the same time. This implies that all members of a cluster have the same view.
6. What is an OCFS2?
The OCFS2 is the Oracle (version 2) Cluster File System which can be used for the Oracle Real Application Cluster.
The OCFS2 is the Oracle (version 2) Cluster File System which can be used for the Oracle Real Application Cluster.
7. Which files can be
placed on an Oracle Cluster File System?
- Oracle Software installation (Windows only)
- Oracle files (controlfiles, datafiles, redologs, files described by the bfile datatype)
- Shared configuration files (spfile)
- OCR and voting disk
- Files created by Oracle during runtime
- Oracle Software installation (Windows only)
- Oracle files (controlfiles, datafiles, redologs, files described by the bfile datatype)
- Shared configuration files (spfile)
- OCR and voting disk
- Files created by Oracle during runtime
Note: There are some platform specific
limitations.
8. Do you know
another Cluster Vendor?
HP Tru64 Unix, Veritas, Microsoft
HP Tru64 Unix, Veritas, Microsoft
9. How is possible to
install a RAC if we don’t have a CFS?
This is possible by using a raw device.
This is possible by using a raw device.
10. What is a raw
device?
A raw device is a disk drive that does not yet have a file system set up. Raw devices are used for Real Application Clusters since they enable the sharing of disks.
A raw device is a disk drive that does not yet have a file system set up. Raw devices are used for Real Application Clusters since they enable the sharing of disks.
11. What is a raw
partition?
A raw partition is a portion of a physical disk that is accessed at the lowest possible level. A raw partition is created when an extended partition is created and logical partitions are assigned to it without any formatting. Once formatting is complete, it is called cooked partition.
A raw partition is a portion of a physical disk that is accessed at the lowest possible level. A raw partition is created when an extended partition is created and logical partitions are assigned to it without any formatting. Once formatting is complete, it is called cooked partition.
12. When to use CFS
over raw?
A CFS offers:
- Simpler management
- Use of Oracle Managed Files with RAC
- Single Oracle Software installation
- Autoextend enabled on Oracle datafiles
- Uniform accessibility to archive logs in case of physical node failure
- With Oracle_Home on CFS, when you apply Oracle patches CFS guarantees that the updated Oracle_Home is visible to all nodes in the cluster.
A CFS offers:
- Simpler management
- Use of Oracle Managed Files with RAC
- Single Oracle Software installation
- Autoextend enabled on Oracle datafiles
- Uniform accessibility to archive logs in case of physical node failure
- With Oracle_Home on CFS, when you apply Oracle patches CFS guarantees that the updated Oracle_Home is visible to all nodes in the cluster.
Note: This option is very dependent on the
availability of a CFS on your platform.
13. When to use raw
over CFS?
- Always when CFS is not available or not supported by Oracle.
- The performance is very, very important: Raw devices offer best performance without any intermediate layer between Oracle and the disk.
Note: Autoextend fails on raw devices if the space is exhausted. However the space could be added online if needed.
- Always when CFS is not available or not supported by Oracle.
- The performance is very, very important: Raw devices offer best performance without any intermediate layer between Oracle and the disk.
Note: Autoextend fails on raw devices if the space is exhausted. However the space could be added online if needed.
14. What CRS is?
Oracle RAC 10g Release 1 introduced Oracle Cluster Ready Services (CRS), a platform-independent set of system services for cluster environments. In Release 2, Oracle has renamed this product to Oracle Clusterware.
Oracle RAC 10g Release 1 introduced Oracle Cluster Ready Services (CRS), a platform-independent set of system services for cluster environments. In Release 2, Oracle has renamed this product to Oracle Clusterware.
15. What is VIP IP
used for?
It returns a dead connection IMMIDIATELY, when its primary node fails. Without using VIP IP, the clients have to wait around 10 minutes to receive ORA-3113: “end of file on communications channel”. However, using Transparent Application Failover (TAF) could avoid ORA-3113.
It returns a dead connection IMMIDIATELY, when its primary node fails. Without using VIP IP, the clients have to wait around 10 minutes to receive ORA-3113: “end of file on communications channel”. However, using Transparent Application Failover (TAF) could avoid ORA-3113.
16. Why we need to
have configured SSH or RSH on the RAC nodes?
SSH (Secure Shell,10g+) or RSH (Remote Shell, 9i+) allows “oracle” UNIX account connecting to another RAC node and copy/ run commands as the local “oracle” UNIX account.
SSH (Secure Shell,10g+) or RSH (Remote Shell, 9i+) allows “oracle” UNIX account connecting to another RAC node and copy/ run commands as the local “oracle” UNIX account.
17. Is the SSH, RSH
needed for normal RAC operations?
No. SSH or RSH are needed only for RAC, patch set installation and clustered database creation.
No. SSH or RSH are needed only for RAC, patch set installation and clustered database creation.
18. Do we have to
have Oracle RDBMS on all nodes?
Each node of a cluster that is being used for a clustered database will typically have the RDBMS and RAC software loaded on it, but not actual data files (these need to be available via shared disk).
Each node of a cluster that is being used for a clustered database will typically have the RDBMS and RAC software loaded on it, but not actual data files (these need to be available via shared disk).
19. What are the
restrictions on the SID with a RAC database? Is it limited to 5 characters?
The SID prefix in 10g Release 1 and prior versions was restricted to five characters by install/ config tools so that an ORACLE_SID of up to max of 5+3=8 characters can be supported in a RAC environment. The SID prefix is relaxed up to 8 characters in 10g Release 2, see bug 4024251 for more information.
The SID prefix in 10g Release 1 and prior versions was restricted to five characters by install/ config tools so that an ORACLE_SID of up to max of 5+3=8 characters can be supported in a RAC environment. The SID prefix is relaxed up to 8 characters in 10g Release 2, see bug 4024251 for more information.
20. Does Real
Application Clusters support heterogeneous platforms?
The Real Application Clusters do not support heterogeneous platforms in the same cluster.
The Real Application Clusters do not support heterogeneous platforms in the same cluster.
21. Are there any issues for the interconnect when sharing the same switch as the public network by using VLAN to separate the network?
RAC and Clusterware deployment best practices suggests that the interconnect (private connection) be deployed on a stand-alone, physically separate, dedicated switch. On big network the connections could be instable.
22. What is the Load
Balancing Advisory?
To assist in the balancing of application workload across designated resources, Oracle Database 10g Release 2 provides the Load Balancing Advisory. This Advisory monitors the current workload activity across the cluster and for each instance where a service is active; it provides a percentage value of how much of the total workload should be sent to this instance as well as service quality flag.
To assist in the balancing of application workload across designated resources, Oracle Database 10g Release 2 provides the Load Balancing Advisory. This Advisory monitors the current workload activity across the cluster and for each instance where a service is active; it provides a percentage value of how much of the total workload should be sent to this instance as well as service quality flag.
23. How many nodes
are supported in a RAC Database?
With 10g Release 2, we support 100 nodes in a cluster using Oracle Clusterware, and 100 instances in a RAC database. Currently DBCA has a bug where it will not go beyond 63 instances. There is also a documentation bug for the max-instances parameter. With 10g Release 1 the Maximum is 63.
With 10g Release 2, we support 100 nodes in a cluster using Oracle Clusterware, and 100 instances in a RAC database. Currently DBCA has a bug where it will not go beyond 63 instances. There is also a documentation bug for the max-instances parameter. With 10g Release 1 the Maximum is 63.
24. What is the
Cluster Verification Utiltiy (cluvfy)?
The Cluster Verification Utility (CVU) is a validation tool that you can use to check all the important components that need to be verified at different stages of deployment in a RAC environment.
The Cluster Verification Utility (CVU) is a validation tool that you can use to check all the important components that need to be verified at different stages of deployment in a RAC environment.
25. What versions of
the database can I use the cluster verification utility (cluvfy) with?
The cluster verification utility is release with Oracle Database 10g Release 2 but can also be used with Oracle Database 10g Release 1.
The cluster verification utility is release with Oracle Database 10g Release 2 but can also be used with Oracle Database 10g Release 1.
26. If I am using
Vendor Clusterware such as Veritas, IBM, Sun or HP, do I still need Oracle
Clusterware to run Oracle RAC 10g?
Yes. When certified, you can use Vendor Clusterware however you must still install and use Oracle Clusterware for RAC. Best Practice is to leave Oracle Clusterware to manage RAC. For details see Metalink Note 332257.1 and for Veritas SFRAC see 397460.1.
Yes. When certified, you can use Vendor Clusterware however you must still install and use Oracle Clusterware for RAC. Best Practice is to leave Oracle Clusterware to manage RAC. For details see Metalink Note 332257.1 and for Veritas SFRAC see 397460.1.
27. Is RAC on VMWare
supported?
Yes.
Yes.
28. What is hangcheck
timer used for ?
The hangcheck timer checks regularly the health of the system. If the system hangs or stop the node will be restarted automatically.
There are 2 key parameters for this module:
-> hangcheck-tick: this parameter defines the period of time between checks of system health. The default value is 60 seconds; Oracle recommends setting it to 30seconds.
-> hangcheck-margin: this defines the maximum hang delay that should be tolerated before hangcheck-timer resets the RAC node.
The hangcheck timer checks regularly the health of the system. If the system hangs or stop the node will be restarted automatically.
There are 2 key parameters for this module:
-> hangcheck-tick: this parameter defines the period of time between checks of system health. The default value is 60 seconds; Oracle recommends setting it to 30seconds.
-> hangcheck-margin: this defines the maximum hang delay that should be tolerated before hangcheck-timer resets the RAC node.
29. Is the hangcheck
timer still needed with Oracle RAC 10g?
Yes.
Yes.
30. What files can I
put on Linux OCFS2?
For optimal performance, you should only put the following files on Linux OCFS2:
- Datafiles
- Control Files
- Redo Logs
- Archive Logs
- Shared Configuration File (OCR)
- Voting File
- SPFILE
For optimal performance, you should only put the following files on Linux OCFS2:
- Datafiles
- Control Files
- Redo Logs
- Archive Logs
- Shared Configuration File (OCR)
- Voting File
- SPFILE
31. Is it possible to
use ASM for the OCR and voting disk?
No, the OCR and voting disk must be on raw or CFS (cluster file system).
No, the OCR and voting disk must be on raw or CFS (cluster file system).
32. Can I change the
name of my cluster after I have created it when I am using Oracle Clusterware?
No, you must properly uninstall Oracle Clusterware and then re-install.
No, you must properly uninstall Oracle Clusterware and then re-install.
33. What the O2CB is?
The O2CB is the OCFS2 cluster stack. OCFS2 includes some services. These services must be started before using OCFS2 (mount/ format the file systems).
The O2CB is the OCFS2 cluster stack. OCFS2 includes some services. These services must be started before using OCFS2 (mount/ format the file systems).
34. What the OCR file
is used for?
OCR is a file that manages the cluster and RAC configuration.
OCR is a file that manages the cluster and RAC configuration.
35. What the Voting
Disk file is used for?
The voting disk is nothing but a file that contains and manages information of all the node memberships.
The voting disk is nothing but a file that contains and manages information of all the node memberships.
36. What is the
recommended method to make backups of a RAC environment?
RMAN to make backups of the database, dd to backup your voting disk and
hard copies of the OCR file.
37. What command would you use to check the availability of the RAC system?
crs_stat -t -v (-t -v are optional)
38. What is the minimum number of instances you need to have in order to create a RAC?
You can create a RAC with just one server.
39. Name two specific RAC background processes
RAC processes are: LMON, LMDx, LMSn, LKCx and DIAG.
crs_stat -t -v (-t -v are optional)
38. What is the minimum number of instances you need to have in order to create a RAC?
You can create a RAC with just one server.
39. Name two specific RAC background processes
RAC processes are: LMON, LMDx, LMSn, LKCx and DIAG.
40. Can you have many database versions in the same RAC?
Yes, but Clusterware version must be greater than the greater database version.
Yes, but Clusterware version must be greater than the greater database version.
41. What was
RAC previous name before it was called RAC?OPS: Oracle Parallel Server
42. What RAC
component is used for communication between instances?Private Interconnect.
43. What is the
difference between normal views and RAC views?A RAC view has the prefix ‘G’. For example,
GV$SESSION instead of V$SESSION
44. Which
command will we use to manage (stop, start) RAC services in command-line mode?
srvctl
srvctl
45. How many
alert logs exist in a RAC environment?
A- One for each instance.
A- One for each instance.
46. What are Oracle
Clusterware Components
Voting Disk — Oracle RAC uses the voting disk to
manage cluster membership by way of a health check and arbitrates cluster
ownership among the instances in case of network failures. The voting disk must
reside on shared disk.
Oracle Cluster Registry (OCR) — Maintains cluster configuration
information as well as configuration information about any cluster database
within the cluster. The OCR must reside on shared disk that is accessible by
all of the nodes in your cluster
47. How do you backup
voting disk
#dd if=voting_disk_name of=backup_file_name
48. How do I identify
the voting disk location
#crsctl query css votedisk
49. How do I identify
the OCR file location
check /var/opt/oracle/ocr.loc or /etc/ocr.loc (
depends upon platform)
or
#ocrcheck
or
#ocrcheck
50. What is SCAN?
Single Client Access Name (SCAN) is s a new
Oracle Real Application Clusters (RAC) 11g Release 2 feature that provides a
single name for clients to access an Oracle Database running in a cluster. The
benefit is clients using SCAN do not need to change if you add or remove nodes
in the cluster.
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