Veritas Cluster (VCS) Questions

1.How do check the status of VERITAS Cluster Server ?
Ans: hastatus –sum

2. Which is the main config file for VCS and where it is located?
Ans: main.cf is the main configuration file for VCS and it is located in /etc/VRTSvcs/conf/config.

3. Which command you will use to check the syntax of the main.cf ?
Ans: hacf -verify /etc/VRTSvcs/conf/config

4. How will you check the status of individual resources of VCS cluster?
Ans: hares –state

5. What is the service group in VCS ?
Ans: Service group is made up of resources and their links which you normally requires to maintain the HA of application.

6. What is the use of halink command ?
Ans: halink is used to link the dependencies of the resources

7. What is the difference between switchover and failover ?
Ans: Switchover is an manual task where as failover is automatic. You can switchover service group from online cluster node to offline cluster node in case of power outage, hardware failure, schedule shutdown and reboot. But the failover will failover the service group to the other node when VCS heartbeat link down, damaged, broken because of some disaster or system hung.

8. What is the use of hagrp command ?
Ans: hagrp is used for doing administrative actions on service groups like online, offline, switch etc.

9. How to switchover the service group in VCS ?
Ans: hagrp  -switch (service_group)  -to (system_name)

10. How to online the service groups in VCS ?
Ans: hagrp  -offline (service_group)  -sys (system_name)

11.What is jeopardy in vcs
The state in which a node is missing one of the two required heartbeat connections. When a node is running with one heartbeat only (in jeopardy), VCS does not restart the applications on a new node. This action of disabling failover is a safety mechanism that prevents data corruption.

12.What is split brain in vcs
Ans : A split brain occurs when two independent systems configured in a cluster assume they have exclusive access to resource. this scenario can be caused when all cluster heartbeat links are simultaneously lost.  Each cluster node will then mark the other cluster node as FAULTED. , usually resulting in data corruption.

13. Cluster Log File location
/var/VRTSvcs/log/engine_A.log

14 . command to  Verifying that links are active for LLT
 Ans:   lltstat –n

15. How can I shutdown VCS without shutting down my applications?
        Ans :-    (1) hastop -all -force  (shuts down VCS on all nodes)
                       (2) hastop -local -force  (shuts down VCS on the local node only)

 13. What's the difference between Agents and Resources?
Ans :    Agents are VCS processes that control and monitor the Resources. Resources are all those objects in your  Service Group, and they all require Agents         

 14.how to Change configuration to read/write mode
Ans :- haconf –makerw

15. what is freeze in vcs
Ans Freeze a service group to prevent it from failing over to another system.

16. Can I run different versions of VCS in the same cluster? 
Ans :- No, absolutely not! Different versions of VCS, and even different patch levels of VCS, cannot run at the same time in the same cluster. Therefore, when you install VCS patches, you must install them on *all* nodes at the same time!

17.Difference in critical and non-critical  resource
Ans :-  1.(NON-critical ) resource fails , service group will not fail over
             2.(Critical ) resource fails , service group will fail over

18. Command to clear the faulty resource
Ans hares -clear (resource-name)  -sys  (faulted-system)

19.  what is the command to Starting and stopping LLT
Ans      lltconfig -c
             lltconfig -U
20 .Starting and stopping GAB
Ans     gabconfig -c -n seed_number
           gabconfig –U

21.  command to check vcs licence
   Ans vxlicense –p

22. command  to list the list the parameters of a resource
Ans   hares -display <resource>

23. command to freeze the service group
  Ans    hagrp -freeze <service group>