CICS resources
Before you can run a program in CICS, you must supply CICS with information about system resources, including software resources such as programs and data, and hardware resources such as terminals or communications links. At a minimum, you must define a transaction.
Every resource is defined with a set of attributes. The attributes are the properties of the resource, telling CICS®, for example, whether a file can be updated, what security level should be given to a transaction, or the remote systems with which CICS can communicate.
Resource definitions held on the CSD are organized into groups and lists. A group is a collection of related resources on the CSD. Each resource that you define must belong to a group; you cannot define a resource without naming the group. A list contains the names of groups that CICS installs at an initial or cold start. You can add groups to lists if you want them installed at an initial or cold start, or if it helps you to manage your groups better. Groups do not have to belong to lists, and can be defined independently.
Where resources are held
The CICS system definition (CSD) file is a VSAM data set that contains a resource definition record for every resource that is defined to CICS through CEDA, CICS Explorer, or DFHCSDUP.
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 with different CICS regions, including regions at different releases. For information on defining the CSD, see Setting up the CICS system definition data set.
Resources that cannot be defined in the CSD are held in CICS control tables. 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.