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RMAN behavior and finding parent backup (level0) of an incremental backup

User_UAEUZDec 13 2018 — edited Dec 18 2018

Hi all,

I have quite a simple backup strategy

1) fullbackup level 0 - Saturday

2) cumulative incremental level 1 -  Any other days

3) Retention period - 1 month

Q1) How do I find/confirm the parent of an incremental level 1 backup ?  (e.g. how do i confirm the parent backup of the inc backup done on Wednesday)

Q2) On Week3 Saturday, i encounter a disk space issue and my level 0 fullbackup fail partially (3 out of 4 backupset created,  the 4th backupset failed).

On the next day, Sunday - when the next cumulative incremental backup run,  how will RMAN/Oracle behave ? 
Does it based the incremental backup using the 3 x level 0 backupsets that were created successfully yesterday; and for those datafiles in the 4th backupset (which failed yesterday), it will base the incremental backup on the previous week (Week2 Saturday) level 0 backup ?

Regards,

Noob
This post has been answered by top.gun on Dec 13 2018
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Comments

Dude!

Keep in mind that the default for the control_file_record_keep_time init parameter is 7 days. If you use a RMAN retention period of 1 month, you need to adjust the value accordingly, e.g. 35 days. Otherwise you risk loosing RMAN information and your retention policy cannot work.

When RMAN does a level 1 backup and no previous level 0 backup is found, then RMAN will automatically perform a level 0 backup instead of a level 1 backup.

1 person found this helpful
top.gun
Answer

1) This command tells you everything you need to know:

restore database preview summary until time 'sysdate';

2) RMAN will source anythng missing from the latest backup, from the previous backup.

So RMAN will recognise the 3 latest L0 backupsets, and the 4th that is missing will be sourced from the previous Saturday.

The cumulative L1 backup will be a mixture of blocks since last Saturday, and the previous Saturday.

Marked as Answer by User_UAEUZ · Sep 27 2020
1 person found this helpful
User_UAEUZ

Hi Dude,

Thanks for your reply.

If i am using a RMAN catalog,  do i still need to set the control_file_record_keep_time to more then 7 days ?

Regards,

Noob

User_UAEUZ

Hi TopGun,

Thanks for the wonderful command.

From the preview, i see that one of incremental backup is done really base on a previous Saturday L0 backup.

Thank you!

Dude!

yes.

https://docs.oracle.com/cd/B19306_01/backup.102/b14191/rcmcatdb.htm#CIHECBCG

1 person found this helpful
User_UAEUZ

Hi Dude,

Thanks for your reply and the doc link.  It mentioned ->

If you maintain a recovery catalog, then use the RMAN RESYNCCATALOG command often enough to ensure that control file records are propagated to the recovery catalog before they are reused.
Make sure that CONTROL_FILE_RECORD_KEEP_TIME is longer than the interval between backups or resynchronizations. Otherwise, control file records could be reused before they are propagated to the recovery catalog. An extra week is a safe margin in most circumstances.

I am doing backup daily, and i think when i connect to the rman catalog , it will auto sync the controlfile backup information to the catalog - right ?

If that's the case, why would i stlil need to extend the CONTROL_FILE_RECORD_KEEP_TIME ? (since everyday during backup, the backup information from contorlfile will be sync to the catalog)

Regards,

Noob

Dude!

You must ensure that you resynchronize the recovery catalog with the control file records before these records are erased. For example, if the rman retention is 1 month, control_file_record_keep_time default, then if backup the database only every 2 weeks, information will be incomplete, regardless of the retention setting and using a catalog database.

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Added on Dec 13 2018
#performance-availability, #recovery-manager-rman
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