Dynamically deleting tape devices from MIA's control

Products

MIM Resource Sharing (MIM) MIM Tape Sharing (MIA)

Issue/Introduction

The focus of this document is providing a procedure for dynamically deleting tape devices that MIA manages using z/OS ACTIVATE.

Environment

Release: 12.5
Component: MIA-Tape Sharing

Resolution

Resynchronization is the MIA process by which you can dynamically change the devices defined to MIA for management. To dynamically remove devices from MIA device management, you can trigger the MIA resynchronization process in 1 of 2 ways - by issuing the MIA RESYNCH command or by performing a deleting z/OS ACTIVATE. The MIA internal process is the same for both of these.

If you are removing tape devices from MIA device management without doing a z/OS ACTIVATE, then you will manually issue the MIA RESYNCH command. The MIA RESYNCH command is documented in the MIM Statement and Command Reference, so the description and use of this command will not be duplicated here. All MIM manuals are available for viewing online or for downloading as a PDF file.

If you will be performing a z/OS ACTIVATE to delete tape devices, then MIA will detect the ACTIVATE and automatically perform a resynchronization. The rest of this document describes the process of setting up MIA prior to performing a deleting z/OS ACTIVATE. Here is a summary of the steps:

Verify the current MIA initialization settings for managing tape devices.
Verify the current MIA command settings for resynchronization.
Decide how MIA will manage tape devices after resynchronization and set the appropriate values.
Initiate z/OS ACTIVE.

Verify the current MIA initialization settings for managing tape devices.
To begin, you should be aware of how you currently instruct MIA to manage tape devices on the MIMINIT initialization statement. You can verify this by issuing MIM command DISPLAY MIM INIT. The command response will identify the values currently in effect for the DEVCLASS and DEVLIST initialization parameters. DEVCLASS can specify TAPE or NONE. DEVLIST can specify NONE or it can specify a MIMPARMS member name in which device definition statements have been coded.

Specifying DEVCLASS=TAPE instructs MIA to manage the entire class of tape devices. Using DEVLIST to specify a MIMPARMS member provides MIA with a list of select tape devices to manage. The default member name, and the name by which we commonly refer to the DEVLIST member, is MIMUNITS but you can use any valid PDS member name. Most customers will specify 1 of the following 2 options:
1. DEVCLASS=TAPE and DEVLIST=NONE
2. DEVCLASS=NONE and DEVLIST=membername
It is very uncommon to specify DEVCLASS=TAPE and DEVLIST=membername, but is typically done to manage all tape devices while using a device list to assign global names to devices.
Verify the current MIA command settings for resynchronization.
Next, verify the parameters specified on the MIA settable option called RESYNCH. Do this by issuing MIA command DISPLAY GTAF OPTIONS. Part of the output will look similar to this:
```
     - CURRENT RESYNCH OPTIONS:                                      DEVCLASS=NONE         DEVLIST=MIAUNITS      COMMANDS=NONE     SAMEDEVS=NO    
```
The RESYNCH options will be used by MIA when either manual (RESYNCH command) or an automatic (z/OS ACTIVATE) resynchronization occurs. To briefly describe the RESYNCH options:

*DEVCLASS and DEVLIST - These parameters have the same meaning here as when specified on the MIMINIT statement.
* SAMEDEVS - This option specifies whether you want MIA to continue managing only the same devices it was managing prior to resynchronization. The value for SAMEDEVS is not important here, because SAMEDEVS is applicable only to adding tape devices.
*COMMANDS - This parameter identifies a MIMPARMS member that can be used to issue commands when resynchronization completes. The COMMANDS member is typically a single-use member that contains MIA VARY commands. This COMMANDS member is not intended to be the same member as your existing MIMCMNDS or MIMSYNCH members. This member is useful for issuing VARY ONLINE commands when adding devices, but it is generally set to NONE when deleting devices.
Decide how MIA will manage tape devices after resynchronization and set the appropriate values.
Below are the options that you can set for when MIA performs automatic resynchronization. You would issue the corresponding SET command prior to the z/OS ACTIVATE, and use MIM command D GTA OPT to verify your settings.

If you will be using a DEVLIST member following resynchronization, but the member includes devices that were just deleted, then MIA will issue message MIM2002 for each deleted device. The text of MIM2002 states INVALID ENTRY IN THE DEVICE CONTROL MEMBER - 'devaddr' NOT IN GEN. You can avoid the MIM2002 messages by removing from the DEVLIST member the devices to be deleted before initiating z/OS ACTIVATE.

All of the options below are shown with the defaults of COMMANDS=NONE and SAMEDEVS=NO. You may choose to provide a COMMANDS member, but SAMEDEVS is not applicable to deleting managed devices.
1. I use DEVCLASS=TAPE and I want to continue using DEVCLASS=TAPE.
  Use this MIM command: F MIM,RESYNCH=(DEVCLASS=TAPE,DEVLIST=NONE,COMMANDS=NONE,SAMEDEVS=NO)
2. I use DEVCLASS=TAPE but I don't want to continue using DEVCLASS=TAPE.
  Use this MIM command: F MIM,RESYNCH=(DEVCLASS=NONE,DEVLIST=membername,COMMANDS=NONE,SAMEDEVS=NO)
3. I use a DEVLIST member and I want to continue using a DEVLIST member.
  Use this MIM command: F MIM,RESYNCH=(DEVCLASS=NONE,DEVLIST=membername,COMMANDS=NONE,SAMEDEVS=NO)
4. I use a DEVLIST member but I don't want to continue using a DEVLIST member.
  Use this MIM command: F MIM,RESYNCH=(DEVCLASS=TAPE,DEVLIST=NONE,COMMANDS=NONE,SAMEDEVS=NO)
Initiate z/OS ACTIVE.
Once you issue the appropriate SET RESYNCH command and verify the settings with the D GTA OPT command, you can then initiate the z/OS ACTIVATE. Devices to be deleted should already be offline prior to starting z/OS ACTIVATE.

Reminder - z/OS ACTIVATE is a local process that affects devices only on the system where it executes. The MIA resynchronization process is also local in scope, regardless of whether resynchronization occurs automatically as a result of z/OS ACTIVATE or is initiated manually as a result of the MIA RESYNCH command.

If you deleted tape devices that had been managed by MIA, and you did not already remove the devices from your MIMUNITS, you can do so now. This will avoid MIM2002 messages on subsequent restarts of MIA. You may also want to remove any VARY commands which you may have for the deleted devices in your MIMSYNCH member.

The only problem to be aware of involves a deleting ACTIVATE when the delete fails with REASON=0151 and has text that states MIM2098 DEVICE PINNED BY MIA. If encountered, see the following knowledge article.

https://knowledge.broadcom.com/external/article?articleId=50859

The original documentation source for the MIA resynchronization process is the MIA Programming Guide. For additional information on MIA resynchronization, refer to Advanced Topics section called Dynamically Change Which Devices Are Managed.