This article provides basic guidelines on how to change Hostname from VCS' perspective only, if one would like to change hostname for Volume Manager too, then please consider reviewing this article 000038038. It's also advisable to review VCS admin guide to understand hostname or other attribute details on VCS cluster. 

We would require to update /etc/llttab, /etc/llthosts, /etc/VRTSvcs/conf/sysname, /etc/VRTSvcs/conf/config/main.cf etc. files. 

The process would be as follows:

1. Make sure the current VCS   configuration is written to disk and changes the configuration to read-only mode.

# haconf -dump -makero

2. Stop VCS while Service Group running.

# hastop -all -force 

3. Unconfigure GAB driver

# gabconfig -U

4. Unconfigure LLT driver

# lltconfig -U

5. Update these files with appropriate hostname /etc/llttab, /etc/llthosts, /etc/VRTSvcs/conf/sysname, /etc/VRTSvcs/conf/config/main.cf etc. on all the cluster nodes. 

Note - main.cf contains generally the followings attributes - SystemList, AutoStartList, CVMNodeId etc. depending on the configuration setup.

6.Verify the main.cf

# hacf -verify /etc/VRTSvcs/conf/config

7. Configure LLT protocol from /etc/llttab on each cluster nodes.

# lltconfig -c

8. Configure GAB driver 

# gabconfig -c -n2 (for 2 node cluster)

9. Verify that LLT and GAB are running on all systems (this should show port a running on both nodes

# lltstat -nvv active

# gabconfig -a

GAB Port Memberships
===============================================================
Port a gen   741f01 membership 01

10. Start VCS where we modified the main.cf, followed by hastart on the rest. 

# hastart

gabconfig -a should now show all nodes.

 # gabconfig -a

GAB Port Memberships
===============================================================
Port a gen   741f01 membership 01
Port h gen   741f03 membership 01