RAC interview Questions
ASM supports external. normal, high redundancy
Can I create a RAC instance with out ASM
ans: yes, you can create a RAC without ASM by using shared file system, RAW devices or third party storage management software.
with ASM we can achive dynamic redundancy,rebalancing,Automatic storage allocation.
Yes, it is still supported with newer versions starting for 10g,11g,12c,18c,19c
Split brain syndrome - network heart beat , node fencing
Can I create a RAC instance with out ASM
ans: yes, you can create a RAC without ASM by using shared file system, RAW devices or third party storage management software.
with ASM we can achive dynamic redundancy,rebalancing,Automatic storage allocation.
Yes, it is still supported with newer versions starting for 10g,11g,12c,18c,19c
Split brain syndrome - network heart beat , node fencing
Cache fusion - GRD (role and mode of the resource ) - role -> current role/interested role -> exclusive /shared -> read/read -> read/write -> write/write
what does root.sh script does in Oracle RAC?
ANS: It will perform certain taks like creating required directories,creating the network settings for inter node comunication,setting up environmental variables
also it will configure clusterware and listener
what are the directories created by root.sh script?
oracle home , oracle inventory,crs home, OCR and voting disk location
How to check the location of OCR and voting disk ?
ocrcheck
crsctl query css votedisk
crsctl query css votedisk --state
what does OCR contains ?
OCR contains information about cluster configuration data like node memebership, network settings..etc , resource configuration data like ASM,DB,servcies, voting disk information
how to enable automatic backup for OCR?
ocrconfig --autobackup on --backuploc /u01/app/oracle -frequency daily recycle -7 -starttime "5:00"
how to restore OCR from a backup?
ocrconfig -restore /u01/app/backup_ocr
ocrconfig -remotereplicate node2
I have lost a voting disk, how to do I attach a new one?
check the status of the votedisk
crsctl query css votedisk --state
create a new volume using fdisk,pvcreate,vgextend
ocrconfig add +DGVD
what is the differfence between OLR and OCR?
OLR contains node specific information and it is specific to the node like it contains information of node settings , its resource information
How to add a new network interface for a node?
-> login to the node
-> add the new interface eth1
-> you can cross check using ifconfig
-> crsctl add network eth1 -subnet 192.168.1.20/24
How a node is determined as primary node during the startup of RAC?
CRM process is responsible to determine the primary node of the cluster using quorom based algorithm , the node with max number of votes or the node which is having latest cluster timestamps or the node with highest node number
Is it mandortory to have OCR on ASM?
It is not mandatory , but it is recomended to be on ASM as it will have certain AMS features like redundancy, rebalancing,HA
How CRS process reads OCR , when OCR residing on ASM?
CRS process takes the help of OCRD process as it maintains the local copy of OCR and there by starts ASM and CSS at later stage
Can you explain the startup procedure of RAC?
RAc startup process is initiated at OHASD followed by CRS service
CRS service gets information from OCRD process as it maintains the local copy of OCR
now CRS started the ASM instance and also CSS service
CSS services sync the clocks on all the nodes of the cluster and reads OLR on each node
Now CRM service will decide the primary node using quorm algorith and decides the primafry node followed by adding the nodes to the primary node
finally CRS established communication using ONS service to all the nodes of the cluster
what is a VIP?
VIP is important component associated to a RAC cluster , this helps in reducing the network timeout by redireting the connections to surving nodes of the cluster
during a node failure
How many vips are required for 4 node RAC?
typically we need 2 VIPS for each node one for private and one for public .so all in all we need 8 vips
how many scan ips are required for 4 node RAC?
ideally it is recomended to have 1 SCAN for 11gR1
but from 12C onwards we need min 2 SCAN
for a 8 node or more we need min 3 scan vips
How to create a scan VIP?
first determine the DNS and IP address and create as below
open listener.ora and update listener_scan1 listener_scan2 listener_scan3
what is a remote listener?
it is usually have its importance in RAC environment and client ofyten establishes connection using remote listener which is update with scan IP
what is a local listener?
local listener is designed to represent or handles connection requests locally specific to that node.
what is a dynamic listener?
A dynamic listener will help us to reconfigure a listener connection with a new ipadrees and port with out restarting the listener service.
what is a static listener?
It is configured to listen the client connections on a specifc ip and port
what is datagaurd fast_start_failover
It is a technique of automatic failover to standby database in case of abnormal outage at primary site and this achieved by running a process called observer process
what is redoapply?
It is a process of applying redo data to the standby database in synchorous or asyn fashion , ideally defined using parameters log_archive_dest_n
what is automatic GAP resolution?
It is an important feature of oracle DG setup as in case of a DR gap , LNS process on standby will make a request to primary to send the missing archives through
LTS and applied by LNS to redo logs at standby site and eventually fill the gaps automatically
why we need standby redo log?
SRL are integral part of DR as it helps in significant data loss at standby side because they are syncned with online redo logs of primary site which means
redo data transferred to standby side are applied immediately to SRL then applied to standby files
what is active datagaurd?
it is a concept of making the standby database in read only mode instead of mount state, this is beeen achived by maintaining a seprate memort structure called
"RTQ -real time query" in the SGA of standby database . this buffer is updated by querying the copied redo data from the online redo logs of the standby database.
It is a kind of query offloading feature and however it worn't works for full table scan infact we still need to tune the standby database
what is cummulative ,differential,incremental
cummulative is from last full backup
differential is for last differential,last full backup during recovery no need to have information about previous backup
differential syntax: BACKUP INCREMENTAL LEVEL 1 CUMULATIVE DATABASE;
incremental: BACKUP INCREMENTAL LEVEL 1 DATABASE;
SQL> SELECT CURRENT_SCN FROM V$DATABASE;
CURRENT_SCN
--------------
3164433
SQL> select min(checkpoint_change#) from v$datafile_header
where file# not in (select file# from v$datafile where enabled = 'READ ONLY');
MIN(F.FHSCN)
----------------
3162298
what is a switchover?
During a switchover primary database send a end of redo signal to standby and stand by will ack with switch over ready
ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY
what anbout failover?
SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY WITH SESSION SHUTDOWN;
SQL> SHUTDOWN IMMEDIATE;
SQL> STARTUP MOUNT;
SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE FINISH;
SQL> ALTER DATABASE OPEN;
SQL> ALTER SYSTEM SET LOG_ARCHIVE_DEST_STATE_2=ENABLE;
what is the disadvantage using auto patch ?
auto patch apply will have lack of control onn your patch process due to customization and also we have to take care of any compatibility issues
what does root.sh script does in Oracle RAC?
ANS: It will perform certain taks like creating required directories,creating the network settings for inter node comunication,setting up environmental variables
also it will configure clusterware and listener
what are the directories created by root.sh script?
oracle home , oracle inventory,crs home, OCR and voting disk location
How to check the location of OCR and voting disk ?
ocrcheck
crsctl query css votedisk
crsctl query css votedisk --state
what does OCR contains ?
OCR contains information about cluster configuration data like node memebership, network settings..etc , resource configuration data like ASM,DB,servcies, voting disk information
how to enable automatic backup for OCR?
ocrconfig --autobackup on --backuploc /u01/app/oracle -frequency daily recycle -7 -starttime "5:00"
how to restore OCR from a backup?
ocrconfig -restore /u01/app/backup_ocr
ocrconfig -remotereplicate node2
I have lost a voting disk, how to do I attach a new one?
check the status of the votedisk
crsctl query css votedisk --state
create a new volume using fdisk,pvcreate,vgextend
ocrconfig add +DGVD
what is the differfence between OLR and OCR?
OLR contains node specific information and it is specific to the node like it contains information of node settings , its resource information
How to add a new network interface for a node?
-> login to the node
-> add the new interface eth1
-> you can cross check using ifconfig
-> crsctl add network eth1 -subnet 192.168.1.20/24
How a node is determined as primary node during the startup of RAC?
CRM process is responsible to determine the primary node of the cluster using quorom based algorithm , the node with max number of votes or the node which is having latest cluster timestamps or the node with highest node number
Is it mandortory to have OCR on ASM?
It is not mandatory , but it is recomended to be on ASM as it will have certain AMS features like redundancy, rebalancing,HA
How CRS process reads OCR , when OCR residing on ASM?
CRS process takes the help of OCRD process as it maintains the local copy of OCR and there by starts ASM and CSS at later stage
Can you explain the startup procedure of RAC?
RAc startup process is initiated at OHASD followed by CRS service
CRS service gets information from OCRD process as it maintains the local copy of OCR
now CRS started the ASM instance and also CSS service
CSS services sync the clocks on all the nodes of the cluster and reads OLR on each node
Now CRM service will decide the primary node using quorm algorith and decides the primafry node followed by adding the nodes to the primary node
finally CRS established communication using ONS service to all the nodes of the cluster
what is a VIP?
VIP is important component associated to a RAC cluster , this helps in reducing the network timeout by redireting the connections to surving nodes of the cluster
during a node failure
How many vips are required for 4 node RAC?
typically we need 2 VIPS for each node one for private and one for public .so all in all we need 8 vips
how many scan ips are required for 4 node RAC?
ideally it is recomended to have 1 SCAN for 11gR1
but from 12C onwards we need min 2 SCAN
for a 8 node or more we need min 3 scan vips
How to create a scan VIP?
first determine the DNS and IP address and create as below
open listener.ora and update listener_scan1 listener_scan2 listener_scan3
what is a remote listener?
it is usually have its importance in RAC environment and client ofyten establishes connection using remote listener which is update with scan IP
what is a local listener?
local listener is designed to represent or handles connection requests locally specific to that node.
what is a dynamic listener?
A dynamic listener will help us to reconfigure a listener connection with a new ipadrees and port with out restarting the listener service.
what is a static listener?
It is configured to listen the client connections on a specifc ip and port
what is datagaurd fast_start_failover
It is a technique of automatic failover to standby database in case of abnormal outage at primary site and this achieved by running a process called observer process
what is redoapply?
It is a process of applying redo data to the standby database in synchorous or asyn fashion , ideally defined using parameters log_archive_dest_n
what is automatic GAP resolution?
It is an important feature of oracle DG setup as in case of a DR gap , LNS process on standby will make a request to primary to send the missing archives through
LTS and applied by LNS to redo logs at standby site and eventually fill the gaps automatically
why we need standby redo log?
SRL are integral part of DR as it helps in significant data loss at standby side because they are syncned with online redo logs of primary site which means
redo data transferred to standby side are applied immediately to SRL then applied to standby files
what is active datagaurd?
it is a concept of making the standby database in read only mode instead of mount state, this is beeen achived by maintaining a seprate memort structure called
"RTQ -real time query" in the SGA of standby database . this buffer is updated by querying the copied redo data from the online redo logs of the standby database.
It is a kind of query offloading feature and however it worn't works for full table scan infact we still need to tune the standby database
what is cummulative ,differential,incremental
cummulative is from last full backup
differential is for last differential,last full backup during recovery no need to have information about previous backup
differential syntax: BACKUP INCREMENTAL LEVEL 1 CUMULATIVE DATABASE;
incremental: BACKUP INCREMENTAL LEVEL 1 DATABASE;
SQL> SELECT CURRENT_SCN FROM V$DATABASE;
CURRENT_SCN
--------------
3164433
SQL> select min(checkpoint_change#) from v$datafile_header
where file# not in (select file# from v$datafile where enabled = 'READ ONLY');
MIN(F.FHSCN)
----------------
3162298
what is a switchover?
During a switchover primary database send a end of redo signal to standby and stand by will ack with switch over ready
ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY
what anbout failover?
SQL> ALTER DATABASE COMMIT TO SWITCHOVER TO PHYSICAL STANDBY WITH SESSION SHUTDOWN;
SQL> SHUTDOWN IMMEDIATE;
SQL> STARTUP MOUNT;
SQL> ALTER DATABASE RECOVER MANAGED STANDBY DATABASE FINISH;
SQL> ALTER DATABASE OPEN;
SQL> ALTER SYSTEM SET LOG_ARCHIVE_DEST_STATE_2=ENABLE;
what is the disadvantage using auto patch ?
auto patch apply will have lack of control onn your patch process due to customization and also we have to take care of any compatibility issues
how to install data patch
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