DBRC coexistence considerations

An IMS 15 Database Recovery Control (DBRC) instance can coexist with an IMS Version 13 DBRC or an IMS 14 DBRC if you install the DBRC coexistence small programming enhancements (SPEs) to the IMS Version 13 or IMS 14 systems, and upgrade your RECON data set to the IMS 15 format by issuing a CHANGE.RECON UPGRADE command. Additional coexistence considerations apply to other DBRC functions.

SPEs are available for IMS Version 13 and IMS 14 that enable the coexistence of the earlier version DBRC with DBRC for IMS 15. With the appropriate SPE installed, IMS 15 and earlier version DBRCs can share the upgraded RECON data set. If the RECON data set has not been upgraded to IMS 15, the SPE has no effect. After the RECON data set has been upgraded, the SPE enables DBRC to convert records to the appropriate release format, depending on whether the record is being written to or the record is being read from the RECON data set. The SPE does not, however, enable the earlier level DBRC for the new functions delivered with DBRC in IMS 15.

The following coexistence SPEs must be installed to the IMS Version 13 or IMS 14 DBRC for coexistence purposes:

Restriction: After a RECON data set is upgraded to the IMS 15 level, it is not accessible to any pre-IMS 15 system that does not have the DBRC Coexistence SPE installed.

The MINVERS level must be set to the lowest level of IMS that uses or shares the RECON data sets.

Attention: Set a region size of 0M for all pre-IMS 15 Log Archive utility (DFSUARC0) jobs when an upgraded RECON data set is used. Unpredictable results can occur for any DBRC job that reads, writes, or changes any RECON record when inadequate storage is available for the job.

DBRC application coexistence considerations

There are two versions of each DBRC API (DSPAPI) macro: Version 1.0 (delivered with IMS Version 9) and Version 2.0 (delivered with IMS Version 10 and later). DBRC applications compiled with the Version 1.0 DSPAPI macros work without modification or reassembly with Version 2.0 of the DBRC API. However, these applications cannot use any of the newer functions (such as AUTH) or newer options (such as READONLY=YES) that are supported in the Version 2.0 macros.

For IMS Version 9, the default version level of the DSPAPI macros is 1.0. For IMS Version 10 and later, the default version level of the DSPAPI macros is 2.0. If a DBRC application that was originally assembled with the version 1.0 macros is reassembled using an IMS Version 10 or later macro library, and does not specify VERSION=1.0, the application might not work as expected because of the default version change.

Recommendation: If the functionality of an IMS Version 9 DBRC application remains unchanged and is reassembled using an IMS Version 10 or later macro library, specify VERSION=1.0 on the DSPAPI macros.

The enhancements in Version 2.0 of the DBRC API are available only with IMS Version 10 and later. These enhancements can be used only by DBRC applications that are compiled with Version 2.0 or later of the DBRC API.

The output blocks for the IMS 15 DBRC API requests contain more information than the output blocks for earlier-version API requests. DBRC applications must use the latest maps to access the additional information.

In a coexistence environment, the RECON data set can be managed (read, updated, and so on) using the functions that each sharing DBRC supports. For example, a shared RECON data set could be:

  • Updated by a DBRC instance using the batch DBRC commands that are processed by the Database Recovery Control (DBRC) utility (DSPURX00), and queried by using the Query requests through Version 1.0 of the DBRC API
  • Updated or queried by an IMS Version 10 or later DBRC using either the batch DBRC commands or API requests through Version 2.0 of the DBRC API

IMS utilities coexistence considerations

The Batch Backout, Log Recovery, and Log Archive utilities must be run on the IMS version that created the logs. For example, an IMS 14 Batch Backout utility cannot back out logs that were created on IMS 15.

The Database Recovery and Change Accumulation utilities must be run on the IMS version that is the same as the highest level of the logs that are being used. For example, an IMS 14 Database Recover utility can use logs that were created on IMS Version 13 or IMS 14, but not on IMS 15.