Dynamic refresh for MIM when applying maintenance

Products

• MIM Resource Sharing (MIM)

Issue/Introduction

We are applying some new MIM PTFs  on our environment.
Is there any dynamic refresh on CAMIMGR that we can perform without stopping it, or do we need to IPL the system?

 

 

Environment

Release : 12.5

Component : MIM

Resolution

MIM has a LOADLIB command that can be used to implement a different LOAD library than what is currently active. In this process, MIM does an internal shutdown, while still ensuring resource integrity, then restarts with the new maintenance. It is less intrusive than an IPL while maintaining the integrity of your environment.

Before using the LOADLIB command, please be aware of the following:

1. Your MIM address space must be configured to use the MIM Restart Manager and any load libraries must be defined as PDS.

2. If you are using virtual control files, be sure you are not entering the LOADLIB REFRESH command on the current VCF master - it should be migrated to a different system first.

3. We recommend that these PTFS be applied to avoid potential problems when issuing the command (see also Additional Information)
RO97775 VCF delays
RO98592 S0D3 REASON=13 AFTER LOADLIB REFRESH
SO07592 RESERVES not converted with LOADLIB REFRESH
SO08094 S0C4 RC=4 MIMDRBGN MIMASCRE
SO13799 ENQ HANG IN MIMEQXGD

The last two correct issues with PE'd PTF SO07592.

This is how it works in a nutshell:

1. You will be adding the new LOAD library to a specific location in the MIMRMFIL (this is either explicitly defined or dynamic)

2. You will issue LOADLIB REFRESHFROM to change from your current LOADLIB to the new one.

An example of the order of commands could be

F MIM,D LOADLIB                            <---see what libraries are in the MIM RMFIL
F MIM,LOADLIB RESETALTERNATE               <--remove the existing alternate library 
F MIM,LOADLIB SETALTERNATE=(new.load,DASD) <---add the new library containing maintenance
F MIM,LOADLIB REFRESHFROM=ALTERNATE        <---refresh MIM with the new library

The display command will show something like

MIM0067I Command DISPLAY 801             
MIM0964I MIM Load Library Display:       
 Type DSName                             
 Init hlq.MIM125.TS1.CBTDLOAD       
 Curr hlq.MIM125.TS1.CBTDLOAD       
 Prim hlq.MIM125.TS1.CBTDLOAD       
 Alt  hlq.MIM125.TS3.CBTDLOAD.T
 SETAPF=Yes                              
 STARTFROM=Initial  

You can have up to 4 different LOAD libraries defined, and commands exist to change the content of any one of those by pointing to the TYPE.  In this example, the first 3 are the same as the current STEPLIB. Pointig to last one, Alt (ALTERNATE),  adds a different library and uses it for the REFRESH.


If you are not familiar with this command, it is recommend that you read up on it. 
These sections in our doc are helpful.

This section of the doc gives an overview of the Dynamic Refresh Feature.
https://techdocs.broadcom.com/us/en/ca-mainframe-software/traditional-management/ca-mim-for-z-os/12-5/release-notes/new-features/new-ca-mim-driver-features.html

This section shows the syntax
https://techdocs.broadcom.com/us/en/ca-mainframe-software/traditional-management/ca-mim-for-z-os/12-5/statement-and-command-reference/general-ca-mim-statements-and-commands/mim-loadlib-command.html

and this section outlines the process  described above, Dynamic Refresh Activation
https://techdocs.broadcom.com/us/en/ca-mainframe-software/traditional-management/ca-mim-for-z-os/12-5/product-maintenance-activation/dynamic-refresh-activation.html

Additional Information

Regarding the recommended PTFs - the described problems have affected a very few customers, so you can issue the command even if they are not applied. The caveat is that if you do hit one of those problems, it is safest to have a plan in place to IPL the system in order to recover as quickly and cleanly as possible.

MIMRMFILE usage
As alluded to above, the MIMRMFIL can be used physically or dynamically.
Physically:
    The MIMRMFIL DD can be added to your MIM STC, pointing to a standard, RECFM=FB,LREC=80 hlq.RMFIL dataset.
     Doing so will retain any dataset names defined to the file across restarts. The risk here is that, if the file is rarely used, obsolete datasets may appear in your APFLIST (see KB 208281). 

Dynamically:
   Using the MIMRMFIL without defining the DD statement  allows for use of all the same commands. The limitation is that it will not hold any of those changes across restarts.

With either implementation, you will want to verify content and make any necessary changes prior to issuing the LOADLIB REFRESHFROM command.