Advanced Topics › Control and Checkpoint File Considerations › Comparison of DASD Control Files and Coupling Facility Structure Control Files

Comparison of DASD Control Files and Coupling Facility Structure Control Files

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. Either type of control file can be dynamically added using the ALLOCATE command, or dynamically removed using the DEALLOCATE command. The MIGRATE command can be used to switch between control file types while CA MIM is active.

However, there are differences in initial set up of the respective control file media types.

DASD Control Files

DASD control files are pre-allocated with a batch job.

Specify the size of the DASD control file and the DASD volume that is to contain the data set in the JCL. Data set placement is critical because CA MIM uses hardware reserves to serialize cross-system access to the primary DASD control file.

You can specify DASD control files in two ways:

• Through DD statements in the CA MIM JCL PROC,
• Using ALLOCATE initialization statements in the MIMINIT member of the MIMPARMS data set.

DASD control files are identified by a ddname of MIMTBLnn, where nn is a numeric value from 00 to 99.

Coupling Facility Structure Control Files

You define coupling facility structure control files in the Coupling Facility Resource Management (CFRM) policy couple data set.

• Use the IBM utility, IXCL1DSU, to allocate and format the CFRM couple data set, if one is not already in use in the parallel sysplex.
• Use the IBM utility, IXCMIAPU, to update the policy information in the CFRM couple data set.
• Issue the following z/OS command to activate the coupling facility policies:

  SETXCF START,POLICY
  

Note: For more information, see the IBM publication Setting Up a Sysplex.

You can identify coupling facility structure control files by using ALLOCATE statements in the MIMINIT member of the MIMPARMS data set. The XESFILEID keyword and the STRNAME keyword of the ALLOCATE statement uniquely specify a control file identifier and a structure name for the control file.