Description

A CASTOUT_DATA request allows you to read a data item from an entry in the cache structure to the storage areas specified by BUFFER or BUFLIST and/or ADJAREA. From these areas, the data can be written to permanent storage such as DASD. This is part of the cast-out process.

When you issue a CASTOUT_DATA request:

A cast-out lock is obtained for the data item specified by NAME. This lock protects the data item from further cast-out processing until the cast-out lock is released. (To release the cast-out lock, you must issue an UNLOCK_CASTOUT request.)
The change indicator in the directory entry for the data item is updated to indicate the data entry contains unchanged data. (Note that the data is considered changed until the cast-out lock is released.)

This request also allows you to register your interest (REGUSER=YES) in the data item. To register or update your interest in a data item, you must specify an index into your local cache vector (VECTORINDEX) to be associated with the named data item in the structure. This index identifies a vector entry that cache services uses to indicate both your interest in the data item and the validity of your locally cached copy of the data item. Having registered interest in the data item means that you have a valid copy of the data item in your local cache buffer. When another user updates the data item in the structure, cache services will update the data item's associated vector entry, thereby deregistering your interest in the data item and invalidating your locally cached copy.