Identifying the Cast-Out Locks to Release

To identify the data items whose cast-out locks are to be released, you build a list of names in a buffer. The mapping macro IXLYCUNB maps each name element in the list. For a description of IXLYCUNB, see z/OS® MVS™ Data Areas in the z/OS Internet library.

Each name element in the list identifies one data item and contains the following information:

Data item name: The name of the data item whose cast-out lock is to be released.
User-defined data: Data that is to replace the current user-defined data in the directory entry for the data item.
Parity bits: Parity bits that are to replace the current parity bits in the directory entry for the data item.
Change indicator: An indicator to allow the system to mark the data item as changed in the cache structure after the lock is released.

When you issue IXLCACHE REQUEST=UNLOCK_CASTOUT, you can release cast-out locks for all data items identified in the list of name elements or for a subset of the data items. To identify the set of data items whose cast-out locks are to be released, use the FIRSTNAME and LASTNAME keywords. Both keywords specify an index value into the list of name elements. Use FIRSTNAME to identify the first element for the first data item in the list that the system is to process and LASTNAME to identify the last element for the last data item that the system is to process. The system starts with the data item indicated by the index for FIRSTNAME and attempts to release the cast-out locks for all data items through the data item indicated by the index for LASTNAME.

For example, you have built a list of seven name elements that identify data items named A, B, C, D, E, F, and G. The name element that identifies data item A starts at buffer offset 1. All other name elements follow in contiguous storage:

To release the cast-out locks for A, B, and C, FIRSTNAME must specify an index of 1 and LASTNAME an index of 3.
To release the cast-out locks for C, D, and E, FIRSTNAME must specify an index of 3 and LASTNAME an index of 5.
To release the cast-out lock for data item G only, FIRSTNAME and LASTNAME both must specify an index of 7.