Where resource definitions are held

Every resource defined to CICS® through CEDA or DFHCSDUP is held on the CICS system definition (CSD) file, which is a VSAM data set.

You can change the contents of the CSD without interfering with a running CICS region that uses the CSD. When you install the definitions in the CICS region, CICS copies the information from the CSD and keeps it in its own storage. You can also change the definitions in the running region by reinstalling them, or add more definitions by installing new resources.

You can define the CSD file as recoverable, so that changes that are incomplete when an abend occurs are backed out. You can also share a CSD file and its resource definitions different CICS regions, including regions at different releases. For information on defining the CSD, see Setting up the CICS system definition data set.

CICS control tables contain resource definition records for resources that cannot be defined in the CSD. The tables and their resource definitions are created by using the CICS table assembly macro instructions. You have to code assembler-language macro statements for each resource to appear in the table, assemble the complete set of macro statements, link-edit the output to produce a load module, and specify the module suffix in DFHSIT. See Defining resources in CICS control tables.