Advanced Topics › Communication Methods › Cross-system Communication Methods › Physical Control File Communication Methods

Physical Control File Communication Methods

CA MIM can use either DASD control files or coupling facility structure control files interchangeably in a DASDONLY or a CTCDASD communication environment. Operationally, the same commands, statements, and messages that apply to DASD control files function similarly with coupling facility structure control files.

CA MIM supports up to 100 control files in any combination of DASD or coupling facility structure. You can dynamically add either type of control file using the ALLOCATE command, or dynamically remove them using the DEALLOCATE command. You can use the MIGRATE command to switch between control file types while CA MIM is active.

There are some differences, however, that are involved with the initial setup of the respective control file media types.

DASD control files are pre-allocated with a batch job. The size of the DASD control file is specified in the JCL as well as the DASD volume that is to contain the data set. Data set placement is critical, because CA MIM uses hardware reserves to serialize cross-system access to the primary DASD control file.

You can create specifications for DASD control files either using DD statements in the CA MIM JCL PROC or using ALLOCATE commands in the MIMINIT member.

You can create specifications for coupling facility control files using ALLOCATE commands in the MIMINIT member.

The DASDONLY method uses a control file located on a shared DASD volume or a list structure on a coupling facility.

When shared DASD volumes are used for control files, the MIMplex systems can consist of sysplexed and non-sysplexed images.

When coupling facility list structures are used for control files, all MIMplex members must be a part of the same parallel sysplex.