Abstract: In the past our recommendation for WebSphere Application Server for z/OS configuration file systems was that each node have its own file system, and that file system be owned by the system on which the node ran. Our reason for making that recommendation was the relatively poor performance of read and write operations when the file system was owned by another LPAR.
With z/OS Release 13 improvements were made in the shared file system performance. To see how those improvements worked within a WAS z/OS environment we constructed a test with WAS z/OS across two LPARs and compared unshared file system performance against shared file system performance.
We saw no appreciable difference between the two. That means z/OS R13 provides shared file system performance improvements that renders our prior recommendation of unshared file systems no longer operative.
Of course, if you have an environment with unshared file systems based on our recommendation from before, then by all means stay with it. There's no reason to uproot existing configurations. But with z/OS R13 the shared file system improvements allow for a shared file system if you are thinking of constructing a new cell.