General migration recommendations

Considerations when versions are skipped

If you are migrating to IMS 15.2 from IMS 14 or earlier, your migration plan must take into account the requirements and enhancements that are introduced into IMS in the versions that you are skipping.

For example, if you are migrating to IMS 15.2 from IMS 14, in addition to the requirements and enhancements of IMS 15.2, your migration plan must also account for the requirements and enhancements that are introduced into IMS in all prior releases of IMS 15.

Review the Release Planning information specific to both the IMS version that you are migrating to and the IMS versions that you are skipping.

General migration recommendations

General migration recommendations for current IMS installations are:

• Contact IBM® Software Support for current installation, migration, and problem resolution information, and ask for PSP for IMS.
• Read the Program Directory for Information Management System Transaction and Database Servers V15.02.00 for the most current hardware requirements, software requirements, prerequisites, and installation information. For general installation information, see IMS Version 15.2 Installation.
• Review the service that has been applied to your current system. Determine if any critical service was released since your copy of the new IMS product was created. If critical service was released, install any that is appropriate for your installation of the new IMS release.
• Review the functions and enhancements for IMS 15.2.
  Recommendation: Enable new functions and enhancements in production only after you have the new release up and running in production with your current IMS configuration. After the new IMS release supports your current configuration in production, then take advantage of new functions.
• Review changes to:
  • SMP/E, distribution, and system data sets
  • System definition macros
  • Log records
  • RECON records
  • Exit routines
  • Cataloged procedures
  • Control statement members in the IMS.PROCLIB data set
  • Utilities
  • Operator commands
  • Operating procedures
  • Messages and abend codes
• Determine the availability of updates to IBM IMS Tools, aids, and related products.
• Prepare a migration plan.
• Prepare a fallback plan. See Fallback considerations for a sample list of items to consider when preparing a fallback plan.
• Apply the appropriate coexistence APARs/PTFs to your existing system. For a list of the coexistence APARs/PTFs, see Overview of coexistence APARs.
• Perform database recovery for any database data sets for which Extended Error Queue Elements (EEQEs) have been recorded in the DBRC Recovery Control (RECON) data set.
• If running the Common Service Layer (CSL) in an IMSplex made up of different versions of IMS, use the latest version of IMS for the CSL address spaces, such as SCI, OM, and so forth.
• Certain target and distribution library data sets must be either a PDS or a PDSE. The ADFSJLIB, SDFSJLIB, and ADFSLOAD data sets must be PDSE data sets. SDFSRESL data set must be a PDS. All other target (SDFSxxxx) and distribution (ADFSxxxx) libraries can be either PDS or PDSE.
  Note: Other execution data sets, such as FORMAT, ACBLIB, and MODBLKS data sets, must be a PDS.
• Back up your system, including:
  • Databases and areas
  • RECON data sets
  • SMP/E data sets, distribution, and target libraries
  Recommendation: Examine Hardware Data Compression (HDC) dictionaries when you migrate to a new release of IMS to determine if they incorporate IMS versions that are now out of service. Although rebinding dictionaries is not required when migrating to a new version of IMS, a gradual refresh of these dictionaries to a current release is a good practice.

• Validate your system definition source. You might want to merge the IVP source with your source.

  The IMS IVP is used after the installation of a new IMS system. The IVP is used to verify the installation of IMS and can be used sporadically afterward.

  The IVP Variable Export utility mitigates the migration of IVP variables values between releases.

• Install the system prerequisites and your new IMS system (including the pre-generation service).

  The complete set of IMS 15.2 modules that are needed for execution are built by a combination of SMP/E processing and running an ALL type of system definition process.

  If needed, you can use the SMP/E GENERATE command to generate the JCL for jobs that build the modules that are not built during the system definition process.

• Install required service that was not included in the pre-generation service.
• Install any needed updates to IBM IMS tools, aids, and related products.
• Upgrade the RECON data set.

• Build application control blocks (ACBGEN).

  Attention: Never use an ACB library built in one version of IMS with an IMS system of another version. You could cause an abend in the IMS control region or you could destroy some or all of your databases. Using an ACB library from one version of IMS with an IMS system of another version is a serious error. Carefully review your fallback plan and JCL. Also, protect your ACB library with RACF® (or an equivalent security product), to make the ACB library impossible to use with an incompatible version of IMS.
• Validate cataloged procedures for users.
• Validate user-created members of the IMS.PROCLIB data set.
• Validate, reassemble, and rebind exit routines and user modifications, especially IMS Connect exit routines and code that uses IMS control blocks, such as database randomizers. Check your exit routines before reassembling. Sequence numbers changed in certain modules in IMS 15.2.
• Validate, reassemble, and rebind user programs that process log records. Some log record formats have changed.
• Validate and update operating procedures (for example, recovery, backup, and restart).
• If necessary, set the appropriate values for the AOIP, CMDP, DYNP, EMHB, FPWP, HIOP, LUMC, and LUMP parameters in the DFSPBxxx member of the IMS.PROCLIB data set to specify an upper limit on the amount of storage a pool can acquire. Specifying a limit is not recommended and should be done only after careful consideration. You can also use the IMS Syntax Checker to validate the values for the DFSPBxxx parameters. Consider the various execution parameters described in this information that can affect performance and migration.
• Ensure that appropriate dynamic allocation members are available to the new environment.
• Ensure that any custom routines and exits are available to the new environment (for example, database randomizers, secondary index parsing routines, and others).

• When using MSC to connect IMS systems with different releases, consider all message types (such as ISC, APPC, and OTMA) and the prefix sizes that accompany them.

  Recommendation: When message queue data sets are used, make the MSGQ LRECL and block sizes identical across all IMS MSC systems. A problem can occur when an IMS system is migrated to a new release that uses messages with larger prefix sizes and new prefix segment types. When messages that contain these new and larger prefixes are sent to an earlier release of IMS, the new, and larger prefixes might not fit the message queues of the earlier release of IMS. This size mismatch can cause problems when the message is formatted and delivered to its destination, especially with MFS.

• Consider other products that can be affected by migration.

  Any product that is dependent on the format and contents of the IMS log or the RECON data set is potentially affected. Examples of affected products or utilities are:

  • IMS Statistical Analysis utility
  • IMS Fast Path Log Analysis utility
  • IMS Log Transaction Analysis utility
  • IMS MSC Log Merge utility
  • CICS®
  • IBM Tools
  • Non-IBM products, including user modifications
• After you start and test the IMS 15.2 system, monitor storage usage in both private/eprivate and CSA/ECSA for differences with previous releases. Make adjustments as necessary.