File control

File control provides a facility for accessing data sets, files, and data tables, using keyed or relative-byte-address (RBA) access through the virtual storage access method (VSAM), the basic direct access method (BDAM), shared data table services and the coupling facility data tables server.

VSAM data sets can be accessed in either RLS or non-RLS mode. RLS mode allows sharing of data sets across a parallel sysplex. File control allows updates, additions, deletions, random retrieval, and sequential retrieval (browsing) of logical data in the data sets. If VSAM is used, access to logical data can be through a VSAM alternate index path, as well as through the base data set.

File control reads from, and writes to, user-defined data sets and data tables, gathers statistics, and acquires dynamic storage for I/O operations. File control uses control information defined by the user in FILE resource definitions, or for BDAM files, DFHFCT macro resource definitions. The control information for all file types is held by CICS® in the internal file control table (FCT). This table describes the physical characteristics of all the data sets, and any logical relationships that may exist between them.