Question: Will online backup impact database performance for DB6 V9.1

Question

Dear All,
I would like to know will online backup impact the database performance? for eg: access will be slower if online backup is currently running. Appreciate if someone can shed some light on this as i'm new to DB6.
I know for oracle it will impact due the performance due to tablespace are locked in backup mode and this will increaes I/O load due to every block is written to redo log during backup instead of just the changes.
Hope to hear from you soon.
Cheers,
Nicholas Chang.

Answer 1

Hello Nicholas,
Here is some additional information on throttling utilities such as online backups:
SET UTIL_IMPACT_PRIORITY command
Changes the impact setting for a running utility. Using this command, you can:
throttle a utility that was invoked in unthrottled mode
unthrottle a throttled utility (disable throttling)
reprioritize a throttled utility (useful if running multiple simultaneous throttled utilities)
Scope
Authorization
One of the following:
sysadm
sysctrl
sysmaint
Required connection
Instance. If there is more than one partition on the local machine, the attachment should be made to the correct partition. For example, suppose there are two partitions and a LIST UTILITIES command resulted in the following output:
ID = 2
Type = BACKUP
Database Name = IWZ
Partition Number = 1
Description = online db
Start Time = 07/19/2007 17:32:09.622395
State = Executing
Invocation Type = User
Throttling:
Priority = Unthrottled
Progress Monitoring:
Estimated Percentage Complete = 10
Total Work = 97867649689 bytes
Completed Work = 10124388481 bytes The instance attachment must be made to partition 1 in order to issue a SET UTIL_IMPACT_PRIORITY command against the utility with ID 2. To do this, set DB2NODE=1 in the environment and then issue the instance attachment command.
Command syntax
>>-SET UTIL_IMPACT_PRIORITY FORutility-idTOpriority----><
Command parameters
utility-id
ID of the utility whose impact setting will be updated. IDs of running utilities can be obtained with the LIST UTILITIES command.
TO priority
Specifies an instance-level limit on the impact associated with running a utility. A value of 100 represents the highest priority and 1 represents the lowest priority. Setting priority to 0 will force a throttled utility to continue unthrottled. Setting priority to a non-zero value will force an unthrottled utility to continue in throttled mode.
Examples
The following example unthrottles the utility with ID 2.
   SET UTIL_IMPACT_PRIORITY FOR 2 TO 0
The following example throttles the utility with ID 3 to priority 10. If the priority was 0 before the change then a previously unthrottled utility is now throttled. If the utility was previously throttled (priority had been set to a value greater than zero), then the utility has been reprioritized.
   SET UTIL_IMPACT_PRIORITY FOR 3 TO 10
Relationship between UTIL_IMPACT_LIM and UTIL_IMPACT_PRIORITY settings
The database manager configuration parameter util_impact_lim sets the limit on the impact throttled utilities can have on the overall workload of the machine. 0-99 is a throttled percentage, 100 is no throttling.
The SET UTIL_IMPACT_PRIORITY command sets the priority that a particular utility has over the resources available to throttled utilities as defined by the util_impact_lim configuration parameter. (0 = unthrottled)
Using the backup utility as an example, if the util_impact_lim=10, all utilities can have no more than a 10% average impact upon the total workload as judged by the throttling algorithm. Using two throttled utilities as an example:
Backup with util_inpact_priority 70
Runstats with util_impact_priority 50
Both utilities combined should have no more than a 10% average impact on the total workload, and the utility with the higher priority will get more of the available workload resources. For both the backup and runstats operations, it is also possible to declare the impact priority within the command line of that utility. If you do not issue the SET UTIL_IMPACT_PRIORITY command, the utility will run unthrottled (irrespective of the setting of util_impact_lim).
To view the current priority setting for the utilities that are running, you can use the LIST UTILITIES command.
Usage notes
Throttling requires that an impact policy be defined by setting the util_impact_lim configuration parameter.
Regards,
Adam Wilson
SAP Development Support