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.