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Log frequence for productive system

Former Member
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Hello!

We use SAP DB (version 7.7) and use auto log function.

We configured the redo log frequence so, that every 10 minutes a new redolog will be written to hardware drive.

Question:

How does this setting (log frequence of 10 minutes) affect the performance of the SAP system?

And which setting (every 10, 20, 30 minutes) should be set for productive system?

kind regards

Accepted Solutions (0)

Answers (1)

Answers (1)

markus_doehr2
Active Contributor
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> How does this setting (log frequence of 10 minutes) affect the performance of the SAP system?

The database kernel will create a savepoint - this will produce I/O. In a normal setup you don't save those logs to the same filesystem/partition/disk than the database so the performance is not impacted.

> And which setting (every 10, 20, 30 minutes) should be set for productive system?

Which settings do you need or what are you trying to accomplish?

Markus

Former Member
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Hello!

Mandy thanks.

The redo logs and DATA have their own partition.

My question is about the log settings. Untill today the redo logs were written to the drive, when the max. size of redo log (appr. 1 GB) has been reached.

Now I changed this settng, so I have every 10 minutes a new redolog file on the hardware drive.

The questions:

Does this frequence (10 minutes) affect the performance of the server (network, SAP system, DB)?

What is the recommended setting to redolog setting for productive systems?

markus_doehr2
Active Contributor
0 Kudos

> My question is about the log settings. Untill today the redo logs were written to the drive, when the max. size of redo log (appr. 1 GB) has been reached.

> Now I changed this settng, so I have every 10 minutes a new redolog file on the hardware drive.

So again my question: Why did you change that? What was the reason to do so?

> The questions:

> Does this frequence (10 minutes) affect the performance of the server (network, SAP system, DB)?

The default max time between database savepoints is 600 seconds - so 10 minutes.

> What is the recommended setting to redolog setting for productive systems?

There is no recommended setting for that, it all depends on what you are trying do. If you want e. g. a shadow database running "after" the production database for 10 minutes, then you use that 10 minutes setup. If you want an hour you configure an hour etc.

It's all based on your setup and what you want to do.

Markus

Former Member
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Hello!

Why did you change that? What was the reason to do so?

My previous situation was that the redo log was written on the hard drive when the max. size of the redo log (1 GB) has been reached. This setting was dangerous, because in case of hardware crash I was lost all the last changes.

Now I am thinking about the change and has changed this setting to 10 minutes and asking about the performance...

lbreddemann
Active Contributor
0 Kudos

>

> > How does this setting (log frequence of 10 minutes) affect the performance of the SAP system?

>

> The database kernel will create a savepoint - this will produce I/O. In a normal setup you don't save those logs to the same filesystem/partition/disk than the database so the performance is not impacted.

No, for a log backup there is no savepoint triggered.

Why would we do that?

This is not Oracle and we do not switch log files here.

As long as the general recommendation to keep the log area and the backup storage apart from the data area of the database, you should not see any kind of performance impact, depending on the log backup frequency.

regards,

Lars

lbreddemann
Active Contributor
0 Kudos

>

> Hello!

>

> Why did you change that? What was the reason to do so?

> My previous situation was that the redo log was written on the hard drive when the max. size of the redo log (1 GB) has been reached. This setting was dangerous, because in case of hardware crash I was lost all the last changes.

Sorry, but that's not possible.

The absolute maximum size of an automatic log backup in MaxDB is half the size of the total log area.

And saving your backups to the same storage as the log or data area is nonsense on it's own right...

> Now I am thinking about the change and has changed this setting to 10 minutes and asking about the performance...

How would backing up more often to the location that might crash increase your data safety?

Backup is all about storing data somewhere else where it's safe.

regards,

Lars