File Definitions

A FILE definition connects the 8-character file name your program uses in EXEC CICS READ/WRITE/REWRITE/DELETE to a real VSAM or BDAM data set on disk.

What a file definition contains

• FILE - the 1 to 8 character name used in EXEC CICS file commands, for example ORDFIL.
• DSNAME - the data set name on disk, for example SHOP.ORDER.KSDS.
• OPENSTATUS - OPEN opens the file at install; CLOSED leaves it closed until you open it with CEMT.
• ADD, BROWSE, DELETE, READ, UPDATE - YES/NO switches controlling which operations are allowed.
• DISPOSITION - SHR shares the data set with other regions; OLD gives this region exclusive use.
• STRINGS - number of concurrent requests the file can handle; too few causes waits.
• LSRPOOLID - which local shared resources pool buffers the file, for performance tuning.
• RECORDSIZE and KEYLENGTH describe the VSAM record layout CICS should expect.

Opening, closing and sharing files

• A file defined OPENSTATUS(OPEN) is ready the moment its group is installed.
• Open or close a file any time with CEMT SET FILE(filename) OPEN or CLOSED - no reinstall needed.
• DISPOSITION(SHR) is normal for files shared between regions; the data set must really be shareable (VSAM SHAREOPTIONS).
• For sysplex-wide record-level sharing, use RLSACCESS(YES) so VSAM RLS handles integrity instead of CICS.
• Closing a file with CEMT while tasks use it waits or fails - quiesce the application first.

Example - define a KSDS and open it: