RMAN FUll backup causes Very HIGH CPU consumption

[Former Member]

Hi Friends,

We have an issue in the online backup which causes a very high CPU  consumption in the system .

Which invariable causes the system to be rebooted as it gets hung.

We have Oracle 11g with RHEL 5.7 in the SAP environment.

We are using RMAN to take the full as well as incremental backup with the TSM as a backup server.

The backup has been running fine for over the year since we implemented RMAN .

See below the screencap for the CPU usage during the time the backup runs:

We have no idea why triggering the online FULL backup causes the high CPU consumption,Any advise would be appreciated.

Regards,

Rakesh

[former_member186811]

Hello Rakesh,

Please check if the Block Change tracking is enabled or not using below command

The current change tracking status can be displayed using the following

query:

SQL> SELECT status FROM
v$block_change_tracking;

If it is not enabled Enable it using below command

SQL> alter database enable
block change tracking;

It will no doubt improves incremental backup performance by recording changed blocks in each datafile in a change tracking file as well as it will also decrese the load on CPU too. If change tracking is enabled, RMAN uses the change tracking file to identify changed blocks for incremental backup, thus avoiding the need to scan every block in the datafile

[Former Member]

Hi,

Having high CPU load during backups are normal.

But in your case, seems this issue is happening in recent days.

Can you give us more details?

How many CPUs you have? (Physical and Logical)

What is the database configuration (Size, number of datafiles, vg config)?

What was the CPU utilization before a month/two while executing the full online backup?

Is there any additional load, during your backup hours?

Regards,

Nick Loy

[former_member182657]

Hi Rakesh,

Please share hardware details & parameters configured for RMAN backup.I also suggest you to go through below links:

http://www.oracle.com/technetwork/database/availability/rman-perf-tuning-bp-452204.pdf

Gouranga's Oracle DBA Blog: Oracle 11gR2 RMAN Backup Compression : with Case study

Regards,

Gaurav

[Former Member]

Thanks Gaurav,

We have VMware Virtual platform

Find the other system details below:

the RMAN configuration is below:

rman_channels = 3

( equal to MAX_SESSION in .utl profile)

backup_dev_type = rman_util

tape_copy_cmd = rman

disk_copy_cmd = rman

rman_parms = "ENV=(XINT_PROFILE=/oracle/<sid>/112_64/dbs/initxxxR.utl,PROLE_PORT=57323,&BR_INFO)"

change in file /opt/tivoli/tsm/tdp_r3/ora64/dsm.sys

compression No

TCPWindowsize

128

TCPBuffsize    128

su - root

cd /usr/sap/<SAPSID>/SYS/exe/run

chgrp dba brbackup brarchive

chmod 6754 brbackup brarchive

Regards,

Rakesh

[Former Member]

It would be a nice to add output of ifconfig command.

[Former Member]

Find the output of the ifconfig below:

Regards,

Rakesh

[former_member188883]

Hi Rakesh,

Are you also compressing the backup ?

Regards,

Deepak Kori

[Former Member]

No Deepak,

We are not using compression.

We have been running with this config even since and we never had any issues.

There was no change in the system whatsoever . But now triggering backup causes the system to crawl.

Regards,

Rakesh