How to perform differential incremental backup with NMDA correctly?

Question

First of all, I would like to let you know about a recently finding about backup in Oracle RMAN (Oracle version 11.2) Officially, according to Oracle manual: RMAN Backup Concepts - 11g Release 2 (11.2) In contrast to a full backup, an incremental backup copies only those data blocks that have changed since a previous backup. You can use RMAN to create incremental backups of datafiles, tablespaces, or the whole database. A full backup cannot be part of an incremental backup strategy; that is, it cannot be the parent for a subsequent incremental backup Our findings (please kindly refer a question in Oracle forum): https://community.oracle.com/thread/4018653 Case 1: For a brand new database (no backup had eve been performed): Suppose the first backup is a RMAN full backup. On the next backup, if a RMAN differential incremental level 1 backup is performed, a differential incremental level 0 backup would automatically performed instead. Case 2: Suppose: On time T1: the database performed a differential incremental level 0 backup On time T2: the database performed a full backup (not incremental level 0). On time T3: the database performed a differential incremental level 1 backup It is found that the backup at T2 would be used as the parent for T3. On RMAN restore it would actually restore the full backup (taken on T2) On RMAN recover, it would restore the incremental backup (taken on T3). If multiple backups (full/level0/level1) were performed in the past, it is not crystal clear and could be confusing. ------------------------------------------------------------------------------------------------ So here is my question about EMC NetWorker: How should weekly incremental backup (level 0) with daily incremental backup (level 1) be configured? I do not want use differential incremental level 1 for backup jobs forever. I would like to configure, say, Sunday to run differential incremental level 0 backup.And differential incremental level 1 backup for other days. Note there is a restriction in NetWorker NMDA: The client + save set name has to be unique. I tried to create multiple clients (on the same DB) with different backup levels: For incremental level 0 backup of testdb1, the client name is database.example.org, and the save set is called RMAN:	estdb1_INCREMENTAL If I create another save set (incremental level 1), the client name is database.example.org and the save set is also called RMAN:	estdb1_INCREMENTAL. In NetWorker, it would complain it is duplicated object and refuse to add the later one. Note the save set name is automatically generated. So I had to create one full backup, save set is: RMAN:	estdb1_FULL And then create one incremental backup, save set is RMAN:	estdb1_INCREMENTAL. Please note according to the Oracle concept / manual RMAN Backup Concepts - 11g Release 2 (11.2) This is not the preferred way or the conceptually incorrect to do so (an incremental level 1 backup to depend on a full backup or the parent is a full backup) Is this the preferred way or what is the best practice? Thanks in advance.

ble1 · Answer

Incremental will always depend on full.

In Oracle (RMAN) world, we only take incr0 which is base backup. I don't use further level 1 as there is hit on restore times.

In your case, your incr0 would be base backup and incr1 would be use that base for subsequent backups.

I think most of the time people are confused as what is the difference between full and incr 0 in Oracle. None unless you take incr 1, but if you plan to take incr 1 then you must have incr 0 and not full. See https://www.pythian.com/blog/rman-full-backup-level-0-incrmental/

If you plan to to have different levels, I suggest you have different RMAN script for each and different client associated with that script - rest is just matter of scheduling at your own liking.

dungkaitai · Answer

So it is not possible to configure weekly level 0 incremental backup and daily level 1 incremental backup using the GUI?

I think this backup method have their use case. Such as backup a very large database. (when Data Domain is not available)

ble1 · Answer

It is possible; you use 2 different clients/groups/schedules/policies. Each is used for RMAN script you call and where you define which level you are using.

In my tests, we found that RMAN backups are fast enough to make always full or incr0 backup only (our biggest pure Oracle DB is around 4TiB and the one under SAP is 7TiB; for last one my group runs some 5 hours which also includes cloning/replication).

NetWorker

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