Compressing Existing Data Sets with zEDC Using Disk™ Backup and Restore

Products

• Disk Backup and Restore - MVS
• DISK BACKUP AND RESTORE- ADD-ON OPTIO
• DISK BACKUP AND RESTORE

Issue/Introduction

While zEDC is activated, the existing data sets can be compressed with zEDC using Disk™ Backup and Restore.

Environment

Release: Disk™ Backup and Restore 12.5

Resolution

This feature is already included in the Disk™ Backup and Restore 14.0 release as an option. The following steps are needed only for the prior releases.

The  existing data sets can be compressed with zEDC using the Disk MOVE utility.

IMPORTANT:
Prerequisites:
Apply the following Disk PTFs:
RO93439 to permit MOVE on multi-volumes
RO95648 to fix 2959 DATASET WITH PREMATURE EOF error 
RO96234 is required for non zEDC archived data set sizes to not increase at restore time. 
SO01468 to permit to support MOVE/COPY of PS-LARGE DATA SETS

For zEDC data sets, it exists an IBM problem which requires some Apars. 
IBM Apars: UA95914 and UA95893 are the fixes for z/OS 2.3. It exists equivalent Apars for z/OS 2.2. Please contact IBM. 

Following are the instructions:

1. Ensure that SMS definition for zEDC compression is done by defining a DATA CLASS.

Data Class Name : COMPZEDC             
Description : ZEDC COMPRESSION         
Data Set Name Type  . . .  : EXTENDED  
  If Extended . . . . . .  : PREFERRED 
  Extended Addressability  : NO        
  Record Access Bias  . .  : USER      
  RMODE31 . . . . . . . .  :           
Space Constraint Relief .  : NO        
  Reduce Space Up To (%)   :           
  Guaranteed Space Reduction: NO       
  Dynamic Volume Count  .  :           
Compaction  . . . . . . .  : ZP        
Spanned / Nonspanned  . .  :           
System Managed Buffer   .  :           
System Determined Blocksize: NO   
 

2. The SMS ACS rules should be coded to permit the use of zEDC.

STORAGE CLASS
The STORAGE CLASS ACS routine does an association with a STORAGE CLASS that will be used to assign the zEDC STORAGE GROUP.
Here is a sample of the rule:
IF (&DATACLAS = 'COMPZEDC' AND &UNIT NE ‘TAPE’) THEN DO
   SET &STORCLAS = 'SCZEDC'                           
END      
 
STORAGE GROUP
The STORAGE GROUP used for zEDC can be an existing one.
The assignment in the STORAGE GROUP can be easily done like this:
/* ----------- ASSIGN STORAGE GROUP TO ZEDC COMPRESSED FILES ----- */ 
IF (&DATACLAS = 'COMPZEDC' AND &STORCLAS = 'STANDARD') THEN DO     
   SET &STORGRP = 'ZEDCSG'                                            
END                                                                   
 

3. Disk makes all sequential data sets be zEDC compressed by simply using the MOVE command. It can also return those data sets back to non zEDC compressed state.

Setting SMSALLOC to Y causes the new DATACLASS to be passed in to your ACS routines.  Using the previous ACS statements will then allow the data set to be compressed.

Note below are sample for single volume data sets, in case you have multi-volumes to move, please consider the following changes to perform:
single volume conversion needs MOVE TOVOL=(vvvvvv),DATACLAS=COMPZEDC,STORCLAS=SCZEDC 
multi-volume conversion needs MOVE DATACLAS=DCZEDC,STORCLAS=SCZEDC

 
Here are samples for each case.
//*  ACTIVE ZEDC FOR SMS                            
//S02MOVE   EXEC DMS                                
//SYSIN    DD *
   FIND DSN=
   MOVE TOVOL=volser,DATACLAS=COMPZEDC                           
//SYSPARMS  DD   *                                  
SMSALLOCY                                           

NB: The TOVOL=volser points to one of the volume residing into the ZEDC STORAGE Group                                                    
 
//*  ACTIVE ZEDC FOR NON SMS                  
//S02MOVE   EXEC DMS                          
//SYSIN    DD *            
   FIND DSN=
   MOVE TOVOL=volser,DATACLAS=COMPZEDC                     
//SYSPARMS  DD   *                            
SMSALLOCY 

NB: The TOVOL=volser points to one of the volume residing into the ZEDC STORAGE Group                                        
 
If you would like to return to a non zEDC data set then use the MOVE as follow.
//* REMOVE ZEDC TO NON SMS                           
//S02MOVE   EXEC DMS                                
//SYSIN    DD *
   FIND DSN=
   MOVE TOVOL=(TSOxxx,TSOyyy)                       
//SYSPARMS  DD   *                                  
SMSALLOCN                                            
Note that the SYSPARM SMSALLOCN is needed to override the SMS information that Disk™ Backup and Restore would use from its record information during the new allocation. Here I use other Management, Storage and Data class than the one setup for zEDC. 

NB: The TOVOL=volser points to one of the volume you would like the data set moved to.

   
//* REMOVE ZEDC TO SMS                              
//S02MOVE   EXEC DMS                                
//SYSIN    DD *
   FIND DSN=
   MOVE MGMTCLAS=TSO,STORCLAS=TSO,DATACLAS=DEFAULT  
//SYSPARMS  DD   *                                  
SMSALLOCY        
    
NOTE: The MOVE does not authorize you to move a data set to its original volume so do not forget to use a POOL or a STORAGE GROUP.

Additional Information

Once returned from zEDC status to non-zEDC, the LISTCAT could show similar to the following information:
 
ACT-DIC-TOKEN----X'NnnnnnnBnnFnnnFnnnnnnnnnnnnFE05FE0DFE0EFE0AFE000000000000000000000000'
 
Dictionary token identifies type of compression
• First two bytes of token

– Generic           Token .10. .000 .... 0000             X’4000’
– Tailored           Token .11. .xxx .... 0000              X’6x00’
– zEDC              Token .11. .000 .... 0001              X’6001’
– Rejection        Token 1... .... .... ....                      X’8000’

 
So the data set is not zEDC compressed, however the Dataclas may have the Hardware compression defined.