How to tune optimizer?

[behlau_carlos]

Hello SAP experts,

we are having a customer written programs, that is accessing table BALHDR.

When I check the SQL trace via ST04, I see it is using the index and performing a range scan.

As our SAP system is based on Oracle/SAP ECC 6 (EHP 5), from my understanding, access to table/indexes are getting also managed by optimizer.

Is there a way to tune optimizer?

I am having a hard time, finding good documentation concerning Oracle/SAP/optimizer concerning its tuning. What I found so far leaves more question marks than it answers.

Some year ago, I had a similar issue and SAP support tuned the optimizer and the performance issues had been resolved.

Thanks for your help pointing me in the right direction …

Best regards

Carlos Behlau

[Former Member · Accepted solution]

Except for keywords Oracle/SAP/optimizer also search for statistics.

For a start:

http://service.sap.com/sap/support/notes/588668

hope this helps

[behlau_carlos · Accepted solution]

Hello Josef,

thanks a lot for the note (I already knew them, but I must missed note 724545 and its follow up notes).

Question: BALHDR is a pretty central table (and it indexes) as it is used for application log (if I am correctly). Would tuning on such a table for a single program would make sense, or would it lead to more unwanted issues?

I also cross checked SAP notes concerning BALHDR and there seems to be some corrections like note 1616768 and its connected notes (or is this just performance improvement concerning the delete program)?

Best regards

Carlos Behlau

[Former Member · Accepted solution]

Well, I wasn't sure whether you already had found the notes. But I  gave it a try.

As for tuning for a single program, there may always be unwanted side effects. But usually advantages should prevail.

One more point, I didn't think of it in my first reply.

Besides tuning optimizer, there are also other ways of tuning, like tuning (i.e. rebuilding) indexes.

For some tables, like BALHDR, if I remember correctly, i found it quite useful, from time to time.

I never did a table reorganization though, as suggested in note 1616768, among other things; this may also be helpful.

Have you already read this note:

http://service.sap.com/sap/support/notes/771929

regards