In Oracle 12c, there are many features and improvements in RMAN – Recovery Manager. One of the improvements is RMAN Multi-Section Backup. In this article, I have explained about this Multi-Section backup and it’s enhancements.
Multi-Section Backup Improvements
- Multi-Section option was introduced in Oracle 11g to handle large Datafiles backups.
- Using this option RMAN can split up or break up a large file into sections during the backup and recovery.
- This improves the performance of backup and recovery of a large Datafiles.
Multi-Section option can be used in Oracle 11g for the below,
- Backup using Backup sets.
- Full Backups using Backup sets.
- Incremental level 0 backups using Backup sets.
Multi-Section option can be used in Oracle 11g for the below,
- SECTION SIZE is the keyword used and each channel will create separate files within the backup sets and backup the database in parallel.
- This option can only be used to backup the Datafiles.
- We can not use this option to backup the Control Files.
In the below example, I am trying to take a backup copy of a datafile with datafile ID 5.
———– ——————————————————————— —————
5 +DATA_GRP/proddb/datafile/example.265.848660933 345.625
But it clearly ended with the error saying that this option is not available with “AS COPY”
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=52 device type=DISK
RMAN-00571: =================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS======
RMAN-00571:=================================================
RMAN-03002: failure of backup command at 02/22/2015 18:08:14
RMAN-06580: the SECBYTES option cannot be used with AS COPY
From Oracle 12c RMAN, Multisection Backups are supported for the below.,
- Backup using Backup sets and Image Copies.
- Full Backups using Backup sets and Image Copies.
- Incremental level 0 backups and higher than level 0
A very important point to note here is,
The following command creates a Multi-Section backup of the database using image copies,
The following command creates Multi-Section level 1 incremental backup,
So now I am going to take a backup copy of a datafile using Multi-Section option.
———– ——————————————————————— —————
2 /vol1/oradata/RMANDB/example01.dbf 358.125
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=44 device type=DISK
channel ORA_DISK_1: starting datafile copy
input datafile file number=00002 name=/vol1/oradata/RMANDB/example01.dbf
backing up blocks 1 through 12800
output file name=/oracle/fast_recovery_area/RMANDB/datafile/o1_mf_example_bgmoq5kt_.dbf tag=TAG20150222T184725
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:03
channel ORA_DISK_1: starting datafile copy
input datafile file number=00002 name=/vol1/oradata/RMANDB/example01.dbf
backing up blocks 12801 through 25600
output file name=/oracle/fast_recovery_area/RMANDB/datafile/o1_mf_example_bgmoq5kt_.dbf tag=TAG20150222T184725
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:07
channel ORA_DISK_1: starting datafile copy
input datafile file number=00002 name=/vol1/oradata/RMANDB/example01.dbf
backing up blocks 25601 through 38400
output file name=/oracle/fast_recovery_area/RMANDB/datafile/o1_mf_example_bgmoq5kt_.dbf tag=TAG20150222T184725
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:04
channel ORA_DISK_1: starting datafile copy
input datafile file number=00002 name=/vol1/oradata/RMANDB/example01.dbf
backing up blocks 38401 through 45840
output file name=/oracle/fast_recovery_area/RMANDB/datafile/o1_mf_example_bgmoq5kt_.dbf tag=TAG20150222T184725
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:03
Finished backup at 22-FEB-15
In the above example, the datafile 2 is of size 358 MB. I have specified to take backup of this datafile with section size 100 MB each. Here the datafile is split in to 4 parts.
Section1 – 1 through 12800 – 100 M
Section2 – 12801 through 25600 – 100 M
Section3 – 25601 through 38400 – 100 M
Section4 – 38401 through 45840 – 58 M (Remaining Size)
The backup of the Datafile 2 has been taken as 4 Sections. It has been highlighted in Red colour. But here only one channel is spawned or allocated.
So what happens when we set PARALLELISM? How Multi-Section backups are handled when using PARALLELISM?
Here is another example where I had configured my default parallelism to 4. So when I take backup, 4 channels are used in parallel.
CONFIGURE DEVICE TYPE DISK PARALLELISM 4 BACKUP TYPE TO BACKUPSET;
new RMAN configuration parameters are successfully stored
released channel: ORA_DISK_1
I am going to take backup of the same datafile 2 and let us see how it works.,
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=44 device type=DISK
allocated channel: ORA_DISK_2
channel ORA_DISK_2: SID=40 device type=DISK
allocated channel: ORA_DISK_3
channel ORA_DISK_3: SID=43 device type=DISK
allocated channel: ORA_DISK_4
channel ORA_DISK_4: SID=58 device type=DISK
channel ORA_DISK_1: starting datafile copy
input datafile file number=00002 name=/vol1/oradata/RMANDB/example01.dbf
backing up blocks 1 through 12800
channel ORA_DISK_2: starting datafile copy
input datafile file number=00002 name=/vol1/oradata/RMANDB/example01.dbf
backing up blocks 12801 through 25600
channel ORA_DISK_3: starting datafile copy
input datafile file number=00002 name=/vol1/oradata/RMANDB/example01.dbf
backing up blocks 25601 through 38400
channel ORA_DISK_4: starting datafile copy
input datafile file number=00002 name=/vol1/oradata/RMANDB/example01.dbf
backing up blocks 38401 through 45840
output file name=/oracle/fast_recovery_area/RMANDB/datafile/o1_mf_example_bgmp0psq_.dbf tag=TAG20150222T185230
channel ORA_DISK_1: datafile copy complete, elapsed time: 00:00:08
output file name=/oracle/fast_recovery_area/RMANDB/datafile/o1_mf_example_bgmp0psq_.dbf tag=TAG20150222T185230
channel ORA_DISK_2: datafile copy complete, elapsed time: 00:00:07
output file name=/oracle/fast_recovery_area/RMANDB/datafile/o1_mf_example_bgmp0psq_.dbf tag=TAG20150222T185230
channel ORA_DISK_3: datafile copy complete, elapsed time: 00:00:07
output file name=/oracle/fast_recovery_area/RMANDB/datafile/o1_mf_example_bgmp0psq_.dbf tag=TAG20150222T185230
channel ORA_DISK_4: datafile copy complete, elapsed time: 00:00:07
Finished backup at 22-FEB-15
Here in the above output, 4 channels are allocated and each channel has handled each section and taken the backup.
Hope this post is helpful..!!! I have also written about the “Table Recovery” one of the RMAN 12c new feature. Please find the below link.,
https://www.oracle-scn.com/table-recovery-in-rman-12c/
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