Mixed Page Group Implementation

Document created by Gary_Cherlet on Dec 11, 2015
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Paul Mak has kindly written up his experience of implementing the use of Mixed Page Groups for one of the IDMS sites that he supports through an outsourcing arrangement. Below you can read the introduction to the complete document which is provided as an attachment.  Thank you for this Paul - I'm sure many DBA's will enjoy reading about your experience with this feature. GaryC


Mixed Page Group Implementation - Introduction

We have a large database PED.FPEN003D-AREA which spreads across 12 files with two files sitting on each 3390-9. It has a number of cross-pointer areas (FPEN004D, 5D, 6D, 7X, 8X, 9X, 13X, 18X) They are all part of segment PED with page group 5.


Over the years we have expanded FPEN003D-AREA, changing its page size several times (keeping the ORIGINAL PAGE SIZE 13680 CHARACTERS). We have also increased its page range a number of times. Now we have reached the capacity limits in the number of database pages and records that applications can access.


The solution is to use Mixed Page Group support.


Mixed Page Group Support was introduced in IDMS release 14.1. It allows a single run unit to access data residing in areas defined to different page groups.  The main restriction is that there can be no chain sets that cross page group boundaries.  However, a new feature,  Mixed Page Group Index (MPGI) was introduced in IDMS release 18.5 which allows the owner and member records within an index set relationship to reside in different page groups.


To take advantage of the MGPI  feature, which supports a database with a user-owned index set or system-owned index in which the owner and member record types are in separate areas associated with different segments that are to be assigned to different page groups, the following may be implemented in parts or in total:


  • Convert a chain set to an index set.
  • Move the member or owner record to a separate area.
  • Move the index structure of a system-owned index into an area different from that of the indexed records.
  • Assign an area to a different segment.
  • Assign a segment to a different page group.
  • Alter a DBNAME to allow mixed page groups.
  • Specify the new auto-READY extension for an area.

See more details here:



Paul Mak

Data Engineer

Mainframe Software

ITO APJ - South Pacific

Hewlett Packard Enterprise