AW: Performance problems after migration to MaxDB

Pertzsch, Christoph christoph.pertzsch at devlogix.de
Fri Feb 2 15:10:01 MET 2007


>Have you recollected your dbstats after the migrate?  You might have to delete the current stats and rerun a stats collection
>Oracle's optimizer ( cost based or other ) don't create indexes on the fly. It uses the tables stats 
>to determine which index would be the best to use. If you're stats are old or don't exist then oracle sits with exactly the same problem. 
This is a basic task after a database migraton. Thanks for the hint, I did forgot this.

To update the stats periodically as basis for oracles optimizer is, what I did mean with "magic".
Sorry for the unconcret approach.

Best regards,
Christoph


-----Original Message-----
From: linux.general-bounces at listserv.sap.com [mailto:linux.general-bounces at listserv.sap.com] On Behalf Of Pertzsch, Christoph
Sent: 02 February 2007 11:46
To: linux.general at listserv.sap.com
Subject: AW: Performance problems after migration to MaxDB

Hi Gert,

we have seen these issues too after a migration from MSSQL -> MAXDB.

One Reason is: Oracle/MSSQL databases are optimizing ongoing database requests due to there statistics of past requests... So, if you have a table without secondary indizies for requests oracle will do this "magically" in background to speedup the requests.
For MaxDB you have to create secondary indizies for tables, where you monitor bad performed requests. Indizies have to create in this way, like select condition is stated in ABAP.
For Select * FOR ALL ENTRIES in itab you have to analyse, which fields are in the itab for create a good 2nd index.

Best regards,

Christoph

__________________________________________________________
Christoph Pertzsch | christoph.pertzsch at devlogix.de
www.devlogix.de    | Telefon: +49 177 3882189


-----Ursprüngliche Nachricht-----
Von: linux.general-bounces at listserv.sap.com [mailto:linux.general-bounces at listserv.sap.com] Im Auftrag von Zuylen, G. van
Gesendet: Freitag, 2. Februar 2007 10:23
An: linux.general at listserv.sap.com
Betreff: Performance problems after migration to MaxDB
Wichtigkeit: Hoch

Hello,

 

After an migration from Oracle 8.1.7 to MaxDB 7.6.01-10 (running on Suse SLES9 SP3 x86-64) we have serious performance problems.

Selects which are done on views and joins are performing very bad, as before on the Oracle database. Also selections with the statement SELECT * FROM <tabel> ALL ENTRIES IN i_tab are bad also.

 

Is there anyone who has some experience with migrations to MaxDB or recognizes this problem. And most important, how this was solved. 

 

With thanks in advance.

 

Best regards,

 

Gert van Zuylen

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