what is GAB port y for
GAB port y is introduced in Veritas Storage Foundation for Oracle RAC and Cluster File System version 6 or later.
CVM uses port y for kernel-to-kernel communication required while shipping I/O from node(s) that might have lost local access to the storage to the nodes in the cluster.
port y gets opened on the node once the node becomes a CVM cluster member (vxconfigd daemon enters in cluster mode).
port y closes once the node leaves CVM.
Example gabconfig -a output:
GAB Port Memberships
Port a gen 1b7701 membership 01
Port b gen 1b7704 membership 01
Port d gen 1b7707 membership 01
Port f gen 1b7712 membership 01
Port h gen 1b7706 membership 01
Port u gen 1b770f membership 01
Port v gen 1b770b membership 01
Port w gen 1b770d membership 01
Port y gen 1b770a membership 01
Please note that I/O shipping is another new feature introduced in Veritas Storage Foundation for Oracle RAC and Cluster File System version 6.