General coexistence considerations

Although IMS 15 can coexist with earlier versions of IMS, general coexistence considerations apply.

IMS 15 can coexist with earlier versions, so existing applications and data can be used without change. Migration and coexistence support is provided for IMS Version 13 and IMS 14.

The following general coexistence considerations apply:

• You must build new application control blocks (ACBs) for all existing program specification blocks (PSBs) and database definitions (DBDs).
• An all-system generation and a cold start are required for online systems (DBCTL, DB/DC, DCCTL). All data sets must be formatted when IMS is initialized the first time. To ensure that the data sets are formatted, specify the FORMAT ALL keywords on the cold start command (/NRESTART CHECKPOINT 0 or /ERESTART COLDSYS).
• If you are installing multiple versions of IMS in the same processor, you can continue to use the prior versions of the IMS SVCs with the prior versions of IMS. However, the IMS 15 SVCs are downward compatible with IMS Version 13 and IMS 14. Only IMS 15 requires the IMS 15 SVCs. The IMS 15 SVCs routines are the same for all IMS 15 releases.
• For DB/DC and DCCTL online systems, the MFS format library is a required data set, regardless of whether MFS is used. DBCTL systems do not require an MFS format library.
• Utilities and logs

  You might need to change programs that process the log because some log records that are created by database changes have been modified. For a list of the log records that are new, deleted, or changed for IMS 15.2, see Log record changes in IMS 15.2.

• Extended checkpoint restriction:  You cannot use extended checkpoint to restart applications across different releases of IMS.