Configuration recommendations

There are two methods to enable the XRC enhanced multiple reader function:

Use the NumberReaderTasks value in the parmlib along with parallel access volume aliases for XRCUTL devices.
Use an explicit number of XRCUTL devices for a given SSID and storage control session name (SCSN) combination.

In the following states, you can enable the function by using either of the methods:

The session is active, with all volumes suspended.
The all volumes suspended state has the following two sub-states:
- The session is suspended and the address space is inactive.
- The session is active and the address space is active.
The session is active, with non-suspended volumes.

The configuration also enables the XRC enhanced multiple reader function. You might have multiple storage control session names for a given SSID. You can use either of the following configurations when enabling the enhanced multiple reader support:

Combine the multiple storage control sessions into an enhanced multi-reader session.
Keep the distinct groups of volumes as primary sessions and add auxiliary sessions to each session.

To convert the primary session into the enhanced mode, issue an XADDPAIR command to the existing XRCUTL volume for the SCSN that is to become the primary storage control session ID (SCID). If you have already merged another storage control session name into the primary session, or have added an additional XRCUTL device, the primary session is converted into enhanced mode.

For the following enablement scenarios, set the PARMLIB value AllowEnhancedReader to Yes before you enable the XRC enhanced multiple reader function.

It is important when configuring an enhanced multiple reader session to choose the primary utility volume that will be used on a permanent basis. The primary utility volume is identified with a 'p' next to the SCID in the XQUERY STORAGECONTROL DETAIL report, and cannot be deleted using XDELPAIR without first deleting all other volumes (data and auxiliary utility) in the ER session group. When you create a new enhanced reader session (on an SSID that is not in the XRC session, or using a new SCSN) the first utility volume added with XADDPAIR becomes the primary utility volume. When you convert a storage control session name (SCSN) from a single reader to an enhanced reader, the first utility volume that is re-added with the XADDPAIR command becomes the primary utility. When you combine multiple SCSN's in an SSID, the first utility volume added becomes the primary and the subsequent volumes are merged into the ER group as auxiliary utilities.