Preallocation of ADS for DEDB created by DDL with SDEP defined

In IMS 15, use the PREALLOC= parameter in the DFSDFxxx member to preallocate area data sets (ADS) for data entry database (DEDB) with segment dependent (SDEP) segments defined.

If a DEDB does not have an SDEP, IMS calculates the space of an ADS cluster by using the UOW, ROOT, and SIZE parameters in an AREA statement.

For DEDB that has SDEP segments defined, the PREALLOC= parameter is added to the DDL section of the DFSDFxxx member so that you can choose one of the following ways to define area data sets:

If PREALLOC=YES is defined, pre-allocated area data sets are used.
If PREALLOC=NO is defined, parameters such as CYLINDERS, TRACKS, and VOLUME are used to allocate area data sets.

PREALLOC=NO is the default.

Changes to installing and defining IMS

The PREALLOC= parameter is added to the DDL section of the DFSDFxxx member of the IMSPROCLIB data set.

Changes to troubleshooting for IMS

For a list of the messages and codes that are new or changed for this enhancement, see the IMS messages and codes row in the table in Documentation changes.

For a complete list of all of the new, changed, and deleted messages, and abend codes in IMS 15, see Message and code changes in IMS 15.

Documentation changes

The following table lists the publications that contain new or changed topics for the New function name enhancement. Publications that are not impacted by this enhancement are not included in the table.

Table 1. Links to topics that have new or changed content for this enhancement
Publication	Links to topics
Release planning	General planning information for IMS 15 Changed messages and codes for IMS 15 IMS Version 15 enhancements IMS 15 Database Manager continuous delivery functions Preallocation of ADS for DEDB created by DDL with SDEP defined (new) (this topic)
System definition	DDL section of the DFSDFxxx member
IMS messages and codes	DFS messages	DFS4713E