IDMS Index processing: What happens when reducing the IBC

Products

• IDMS

Issue/Introduction

 What happens at runtime when the Schema/Subschema or AREA Index Symbolic changes, such that the Index Block Contains clause specifies a lower number than was used previously?

Environment

IDMS 19.0

Resolution

  The DBMS has the IBC maximum definition from SS (subschema).   

  When storing a new SR8 the size will be based on the IBC in the current SS.

  Every time an existing SR8 is targeted for an insert of a new member key , DBMS has to check the current number of entries in the SR8 against the max (IBC) to determine if the SR8 can fit a new entry or it must be split. 

  If you decrease the IBC in the Subschema being used to update the database, new SR8s will be based on the IBC in the SS, and when updating existing SR8s if the current number of entries in the SR8 exceeds the SS Max (IBC) that SR8 will be split to conform with the current IBC.