Read locks

Read locks are used to prevent a table entry being deleted by the table manager.

A read lock is a fullword of storage. When DFHKCP attaches a task, it allocates storage for a number of local read locks; this storage is addressed by TCATMRLP in the TCA. Local read locks are not acquired for table entries that cannot be deleted.

Global read locks are used by the CICS® modules that are executed independently of any task. They reside in the table manager static storage area (TMS) that is addressed by SSATMP in the static storage address list (SSA).

These locks are released by:
  • an Unlock call,
  • a Getnext call,
  • a Reset call,
  • the termination of the task,
  • or a DWE call.

Read locks are always obtained against the primary index entry even if the request is against a secondary index or an alias.