Sharing buffers among multiple users

The IVTCSM REQUEST=ASSIGN_BUFFER macroinstruction allows a buffer to be concurrently shared between multiple users. A logical instance of the buffer is created for each user. A new physical copy of the buffer is not created. This function allows specific areas of the buffer to be allocated to different owners. This function can be used to give multiple users read access to the same data.

Tip: No serialization is provided to prevent concurrent updates by users.

A new buffer token that represents the new instance of the buffer is returned. The buffer token is the means by which this new instance of the buffer is known to CSM.

Requirement: This token must be used with all other requests to CSM for the associated buffer instance.

On the ASSIGN_BUFFER request, multiple shared instances of a single buffer can be created by passing a multiple entry buffer list with the same buffer token in each entry.

Restriction: A request to create a new image of a buffer that is in a guaranteed to be pageable state is not permitted. This restriction guarantees that a user of a buffer that has multiple images can successfully issue a FIX_BUFFER request if necessary. Fixing a buffer requires that the entire buffer be fixed regardless of the fact that the user might be interested in only a piece of the buffer. The application can specify the BUFTYPE parameter as described in Fixed buffers versus pageable buffers.