Increase the size of the SCRATCH area

Products

• IDMS
• IDMS - Database

Issue/Introduction

How do you increase the size of the SCRATCH area, DDLDCSCR?

 

 

Resolution

If SCRATCH IN STORAGE YES is specified in the sysgen SYSTEM statement, then there is no physical file used for the SYSTEM.DDLDCSCR.

The SCRATCH IN STORAGE clause has additional parameters defining its location and size. 

If you take the DEFAULT for the size parameters IDMS will allocate a GETMAIN'd area that is as large as the definition for the DDLDCSCR definition in the DMCL ( the default value is the number of pages in the area that is multiplied by the page size). If no scratch area is defined in the DMCL, the system default value is 1 MB.

The best recommendation for increasing the size is to specify specific amounts for Primary Extent, Secondary Extent and Limit.

Example:

 SCRATCH IN STORAGE IS YES  
     LOCATION ANY           
     PRIMARY EXTENT 40 MB   
     SECONDARY EXTENT 20 MB 
     LIMIT 60 MB            

If you take the default for size in the sysgen SYSTEM statement you can increase the size by increasing the number of pages  and/or page size for  SYSTEM.DDLDCSCR.
The SCRATCH IN STORAGE syntax has no means to alter the default page size of 4096. If you need to use a different page size, define a dummy SYSTEM.DDLDCSCR area in the DMCL with the desired page size. You do not need to define a physical dataset - the page size specified in SYSTEM.DDLDCSCR will be used for SCRATCH IN STORAGE anyway.

If you actually use a real physical file for some reason, you would make the definition change for the area, allocate the new larger file, use the updated DMCL to FORMAT the new file and then bring CV up with the new DMCL and pointing to the new file.

Even if you use a physical file, DDLDCSCR is an area that is used only for temporary storage while CV is up. Nothing is maintained across CV cycles so there is never any need to run Unload/Reload or Expand Page utilities for this area. If you need a larger area, you simply make the definition changes, generate, punch, link the updated DMCL, allocate the new larger file and use the updated DMCL to FORMAT the new file before bringing CV up.