Block-level sharing

Block-level sharing requires the Internal Resource Lock Manager (IRLM). If each z/OS® operating system contains an IMS online system participating in block-level sharing, an IRLM component must exist in each z/OS operating system.

IRLM manages all requests for locks that control access to resources participating in data sharing.

Each IRLM responds to the requests that originate from its associated IMS systems. To do this, it maintains records of the participating IMS systems, as well as the status of locks that are held and waiting.

When an IMS online system uses IRLM, IRLM also provides the lock management that controls database resources that are concurrently accessed by application programs within the online system. In this way, the IRLM associated with an IMS online system provides almost all locking services for that system.

The IRLMs communicate with each other and manage the status of locks held for different database locks.

When using IRLM, you must define DBRC-registered SHARELVL=1 VSAM databases to VSAM with the appropriate SHAREOPTIONS required for block-level data sharing. This might require you to make a VSAM definitional change.