Review some of the best practices for using multiple Oracle instances in a VCS environment:
For each SID to be configured, create UNIX accounts with DBA privileges.
Make sure that each Oracle instance has a separate disk group and is configured as a separate service group.
Define the system parameters such that the allocation of semaphore and shared memory is appropriate on all systems.
Use a dedicated set of binaries for each Oracle instance, even if each instance uses the same Oracle version.
If your configuration uses the same Oracle version for all instances, install a version on the root disk or preferably on a secondary disk. Locate the pfiles in the default location and define several listener processes to ensure clean failover.
If your configuration has different versions of Oracle, create a separate $ORACLE_HOME for each Oracle version.
Follow the Optimal Flexible Architecture (OFA) standard (/uxx/<SID>). In cluster configurations, you could adapt the standard to make it more application-specific. For example, /app/uxx/<SID>.
Listeners accompanying different versions of Oracle may not be backward-compatible. So, if you want to create a single listener.ora file, you must verify that the listener supports the other versions of Oracle in the cluster. You must also create a separate Envfile for each version of Oracle.
Make sure that each listener listens to a different virtual address. Also, assign different names to listeners and make sure that they do not listen to the same port.
The pfiles must be coordinated between systems. For the same instance of a database, ensure that the pfiles referenced are identical across the nodes.