Responsibilities of buffer ownership

When an application obtains buffers from CSM on a IVTCSM REQUEST=GET_BUFFER macroinstruction, that application is considered to be the original requester of that storage. Ownership responsibility entails either ultimately freeing the storage (on an IVTCSM REQUEST=FREE_BUFFER macroinstruction) or changing ownership to another user. Failure to return the storage ultimately creates CSM storage constraint conditions.

The original requester of the storage can specify a buffer return exit routine at storage allocation time and is entitled to the return of storage without modification.

Guideline: The receiving application should consider this as read-only storage and should not modify the contents.

If written as a cooperative set of processes, applications might determine that it is acceptable to modify the data if the original application does not require the original data returned unmodified.

Restriction: Applications written in this manner must be able to guarantee that the original requester of the storage is one of the cooperative applications. If the storage allocation source is unknown to the receiver, the read-only requirement applies.