To release a single cast-out lock held by your connection, issue an IXLCACHE REQUEST=UNLOCK_CO_NAME request. After you have (Note that although it is possible to release a single cast-out lock with the UNLOCK_CASTOUT request, it is more efficient to use the UNLOCK_CO_NAME request. After you have cast out and written the data for the data item to permanent storage, you release a cast-out lock. If you fail to update permanent storage for the data item that you have cast out, you need to release the lock, but you indicate that the data item is changed on the UNLOCK_CO_NAME request. As a result, the system does not consider the data item eligible for reclaim. The data item then needs to be cast out again so that you can successfully write the changes to permanent storage.

When you release a cast-out lock for a data item, the system updates the directory entry to indicate that the lock is released. If the data item has not been updated by another user while the lock is held, the system also disassociates the data item from the cast-out class.

As a user, you can also update the directory entry for the data item by providing data for the user-defined data field and by changing the parity bits. You can also indicate on the UNLOCK_CO_NAME request that the system mark the data as changed, which makes the resources unavailable for reclaim.

While you hold a cast-out lock for a data item, another user can write changed data to the data item. If you issue REQUEST=UNLOCK_CO_NAME after another user has changed the data, the system releases the cast-out lock, but does not update the directory entry with any of the data that you provide. Instead, the system considers the data item as changed and updates the directory entry as specified on the write request of the user that makes the change. The data item also remains associated with the cast-out class specified by the user on the WRITE_DATA request.