No system downtime question:

[Former Member]

Hello,

We only run on-line backups here and do not have a scheduled maintenance window.

We have ECC 5.0, BI 7.0 running on Oracle 10 with Solaris.

So SAP or the DB are never re-booted and I was wonderiing what negatives come with not bouncing your system every so often.

I thought you should bounce your system from time to time in order to clear buffers and improve performance.

I appreciate any feedback on this.

Thanks,

Steve

[anindya_bose · Accepted solution]

Hi Steve

Not exactly what you think... SAP buffers and Database buffers quality get detoriarated if you bounce the system. Few hours after bouncing users may get bad response time because SAP's program buffer take some time to get filled. You get best performance when your buffer qualities are as maximum as possible. If you need some program, some SQL statements of any record that is available in buffers ( RAM) then the access is fastest as RAM is much faster than your hard disk.

Even if you fetch some data from database and change it via some program it does not write the changed data directly to database but in the buffer. Then in a specified time DBW0 (database writer) and Log write (LWR0) write these changed information in database. For more information how database works please check TADM51 (SAP's training material)

But, yes with OS restart clears up some memory which is unnecessarily occupied by some unwanted process. An offline backup will bring down your database and SAP but not the OS.

[debasissahoo · Accepted solution]

Hi,

SAP buffers and Database buffers quality get deteriorated if you bounce the system. 
Few hours after bouncing users may get bad response time because SAP's program buffer take some time to get filled.

This is true, except SAP's program buffer. As program buffer has very critical impact on SAP system performance, therefore SAP has made a way to keep the hit ratio high even after instance restart. when SAP is stopped normal process, it writes the name of all program names to a os level file PXANEW (in the work directory of the instance) that are contained in the buffer so that during restart, listed programs are put into the program buffer. So minimizes the impact on system performance becuase of program buffer losing its contents! Refer Note 23642 for futher details.

Best Regards,

Debasis.

[anindya_bose · Accepted solution]

Exactly ..Debasis is right...I forgot about that..Thanks Debasis..

[Former Member]

Thank you all for your reply's they were very helpful.

Steve

[Former Member]

Hi,

For this u may schedulw Database Update Statics twise or once a week. it will help to improove ur performance of Both R3 and BI server. for clearing buffer or other logs and clear temp. space u should take OS Restart once in a month as per ur low activity time.

It will help u lot.

Thanks

Presu

[Former Member]

Hi Steven,

As you said, bouncing the Db then and there will clear up the buffer and thus helps in improving the performance. Make sure that you are bouncing the Db atleast once in a quarter or while applying support packages to avoid DBIF_SQL dumps and also to avoid the FileSystem breakdown or FS corruption or the HDD failure.

We faced similar issue twice in our production server while was running for a while. The first time the HDD failed and the second time the FS corrupted. So it is always better to go for maintenance downtime atleast once in a month to avoid any severe loss of business because of system failure/degradation of the system performance.

Regards,

Varadhu