Procedure to increase a page size using EXPAND PAGE

Products

• IDMS

Issue/Introduction

How to increase the page size of an area by transferring a database file to a new file with an expanded block size.

Environment

Release: All supported releases.

Resolution

1. Decide on a new larger PAGE SIZE for the area. The largest record size in the area needs to be less than 30% of the PAGE SIZE. The actual page size depends on the device type. See the Design Guide for a recommended page size table.

2. Allocate a new dataset file at the new size. This file does not need to be formatted. The file should have the SAME NUMBER OF BLOCKS as the original file (number of pages in the area), and the new block size (new page size).

3. VARY the area offline/retrieval.
   
4. The EXPAND PAGE utility runs in local mode, so no automatic recovery is available. Make a backup copy of the area.

5. EXPAND PAGE syntax: EXPAND PAGE FOR FILE segment.filename INTO NewDDname NEWSIZE ####

 

SAMPLE JCL:

//IDMSBCF  EXEC PGM=IDMSBCF,REGION=2048K                             
//STEPLIB DD DSN=yourhlq.DBA.LOADLIB,DISP=SHR              
//        DD DSN=yourhlq.CUSTOM.LOADLIB,DISP=SHR           
//        DD DSN=yourhlq.CAGJLOAD,DISP=SHR                
//SYSLST   DD SYSOUT=*                                               
//SYSPRINT DD SYSOUT=*                                               
//SORTMSG  DD SYSOUT=*                                               
//SYSUDUMP DD SYSOUT=*                                               
//ORGNEW   DD DSN=yourhlq.NEW5064,DISP=SHR
//SYSJRNL  DD DUMMY                                                  
//SYSIDMS  DD *                                                      
DMCL=yourDMCL                                                        
/*                                                                   
//SYSIPT   DD *                                                      
EXPAND PAGE FOR FILE segment.filename INTO NewDDname NEWSIZE ####;       
/*                                         
 

6.  Once the EXPAND PAGE runs successfully you'll need to modify the existing DMCL. This is best done while the CV is currently up, either online or batch. Change the area's PAGE SIZE to the new page size, and include the ORIGINAL PAGE SIZE clause.

If this is the first time the EXPAND PAGE utility was executed against the area, specify the current PAGE SIZE value as the ORIGINAL PAGE SIZE value.

If this is NOT the first time the area was page expanded, DO NOT change the ORIGINAL PAGE SIZE clause. This value must specify the page size when the page was originally formatted.

7. Regenerate all DMCLs containing the segment of the file, and rename the original DMCL load module that the CV is currently running.

8. PUNCH and LINK the DMCL.

9.  Bring the CV down. RENAME the original dataset name, then rename the file written to by the EXPAND PAGE to the original dataset name that the DMCL uses. In the above example, the EXPAND PAGE wrote to a the file named yourhlq.NEW5064.

10. Find the original dataset name (LOOK DMCL) on the CV's DMCL.

11. Start the CV, when the CV comes up it should load the newly re-genned DMCL.

12. VERIFY the new page size is correct - DCMT D AREA segment.areaname ALL. And VERIFY the data is accessible using PRINT SPACE or an application.

Additional Information

EXPAND PAGE