The purpose of the RESERVE conversion RNL is to convert a hardware RESERVE to just a global (SYSTEMS) ENQ. Even though double serialization (ENQ and hardware reserve) can result in deadlock, it is the default behavior for RESERVE requests. Thus, RESERVE requests should result in only a global ENQ or a hardware reserve and a local (SYSTEM) ENQ.

A hardware reserve request can originated by:

• A task issuing the RESERVE macro or the ISGENQ macro with RESERVEVOLUME=YES
• A task issuing the ENQ macro or the ISGENQ macro with RESERVEVOLUME=NO and a GRS installation exit change the ENQ request to a reserve request by adding a UCB@ to it.

The RESERVE conversion RNL is scanned for all reserve requests under the following conditions:

• A GRS installation exit did not request that RNLs should be bypassed. Note that the RESERVE API does not support RNL=NO.
• After processing installation exits and the exclusion RNL, the ENQ associated with a reserve has a scope of SYSTEMS.

If there is a match, global resource serialization suppresses the reserve for the global resource. It issues an ENQ with a scope of SYSTEMS to serialize access to the resource.

If there is no match, global resource serialization allows the system to issue the reserve. Thus, the RESERVE conversion RNL does not affect the scope of the resource but does determine whether or not the system is to issue the reserve.

Choosing the reserves to be converted is a critical planning task; for a full explanation of the considerations involved, see Potential problems when using RESERVE.

RNLDEF RNL(CONV) TYPE(PATTERN) QNAME(*)