How to dynamically change MIM from DASDONLY DSN to XES list structure

Products

• MIM Resource Sharing (MIM)
• MIM Data Sharing (MII)
• MIM Tape Sharing (MIA)
• MIM Message Sharing (MIC)

Issue/Introduction

This document describes how to change the Control File from DASDONLY using Data Sets to using Coupling Facility List Structures (XES) without cycling MIM.

If all systems in a MIMplex are in the same geographic location and DASDONLY is in use, using list structures has some advantages over DASD Data Sets or switching to XCF when running MII:

1 - FASTER
2 - EASY TO IMPLEMENT - FEW CHANGES REQUIRED
3 - EASIER OPERATIONALLY - NO VCF MASTER FLIP FLOP


Note: MIA and MIC do not have the same performance requirements as MII - it is sufficient for them to use a DASD control file. 

Environment

Release : 12.5

Component : MIM

Resolution

The following sections of the MIM documentation may be helpful to read in advance:

 

1. The Programming Guide provides a wealth of information for this in varying locations.
Here is basic information for setting up an XES control file for a new MIMplex

https://techdocs.broadcom.com/us/en/ca-mainframe-software/traditional-management/ca-mim-for-z-os/12-5/programming/ca-mim-programming/ca-mim-advanced-topics/coupling-facility-structure-control-files-xes.html

 

2. Good background information is a comparison of DASD and List Structure here. You can leave COMMUNICATION=DASDONLY.

https://techdocs.broadcom.com/us/en/ca-mainframe-software/traditional-management/ca-mim-for-z-os/12-5/programming/ca-mim-programming/ca-mim-advanced-topics/control-and-checkpoint-file-considerations/comparison-of-dasd-control-files-and-coupling-facility-structure-control-files.html

 

3. This section shows more detail about the differences between the physical control files

https://techdocs.broadcom.com/us/en/ca-mainframe-software/traditional-management/ca-mim-for-z-os/12-5/programming/ca-mim-programming/ca-mim-advanced-topics/control-file-externals/physical-control-files.html

 

4. XES Control File placement is described here - it has some good additional displays and information.

https://techdocs.broadcom.com/us/en/ca-mainframe-software/traditional-management/ca-mim-for-z-os/12-5/programming/ca-mim-programming/ca-mim-advanced-topics/control-and-checkpoint-file-considerations/how-you-allocate-control-and-checkpoint-files.html#concept.dita_343798c6f2a6fbded491cfd8b24f7689a249af42_XESControlFilePlacement

 

Following is the procedure to switch from DASD to list structures without shutting down.

NOTE: The XESFILEID needs to be sequentially numbered higher than any existing DASD DDNAMEs.
                     Example: If the MIIINIT shows
                        ALLOCATE DDNAME=MIMTBL00,DSNAME=hlq.CF00  
                        ALLOCATE DDNAME=MIMTBL01,DSNAME=hlq.CF01  
                     The XESFILEID's would need to be 02 and 03.

• Use the ALLOCSTR sample JCL to create 2 new list structures. The size of the primary structure can be determined by the DISPLAY CFSIZE command. The alternate List Structure should be 20% larger than the primary.
  
• Update the XCF POLICY to reflect the 2 new list structures
  
• Enter the MIM ALLOCATE command on all systems:
  • *ALLOCATE XESFILEID=02 STRNAME=mim_primary_structure
  • *ALLOCATE XESFILEID=03 STRNAME=mim_alternate_structure
  • *DISPLAY FILES
    
• Confirm that files 02 and 03 are allocated and usable
  
• If so, use the MIGRATE command to migrate to one of them. The command is global so only needs to be entered on 1 system:
  
  • *MIGRATE CF=02
    
• *DISPLAY FILES
  
• Confirm that 02 is now IN-USE
  
• Optionally you can try to migrate to 03 to confirm its operational.
  
• Comment out or delete the ALLOCATE commands for files 00 and 01 in the init member
  
• Add the following ALLOCATE commands in the init member:
  • ALLOCATE XESFILEID=02,STRNAME=mim_primary_structure
  • ALLOCATE XESFILEID=03,STRNAME=mim_alternate_structure