How to keep a certain number of Backup generations?

Products

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

Issue/Introduction

How to keep a certain number of Backup generations?

Environment

Release: SMDI3900200-12.5-Disk-Backup and Restore-for z/OS
Component:

Resolution

For non-SMS data sets you can limit the number of Backup + Archive generations using IXMAINT parameter COPIES=n. 

However, this will still be the maximum number of generations as expired entries are deleted by IXMAINT anyway. 

 

Similar considerations apply also for SMS data sets. 

The following 2 SMS MC attributes define the maximum number of Backup versions: 

- Number of Backup Versions Data set Exists on Primary (MC). 

- Number of Backup Versions Data set Deleted from Primary (MC). 

Also, you can limit the number of Backup + Archive generations for SMS data sets using IXMAINT parameter COPIES=n,SMSNOSMS 

However, this is again the maximum number of generations as expired entries are deleted by IXMAINT due to following 2 SMS MC attributes: 

- Retain Days Only Backup Version Data set Deleted (MC). 

- Retain Days Extra Backup Versions (MC) 

See CA Disk User Guide, chapter "SMS and IXMAINT" for details on these SMS attributes. 

 

So in summary, you can define a maximum number of Backup/Archive generations, for example 3, but you cannot guarantee or retain 3 generations. 

If an entry is expired, it is deleted anyway.