how to tune buffer allocated to index data?

Hi all, I noticed that the buffer allocated to the index data was extremely high in my database (version 7.31.UC2). May I know which parameter (in onconfig) manage this buffer and how to tune it? Percentages: Data 12.16 Btree 86.52 Other 1.32 TIA, Miyaki __________________________________ Do you Yahoo!? Yahoo! Search - Find what you’re looking for faster http://search.yahoo.com

Dear Miyaki, The high percentage of Index pages in the buffer is du to the priority bands that have been introduced in the Informix buffer manager in 7.3x . Index branch pages have a higher priority than data pages and cannot be replaced in the buffer by data pages. This may lead to a situation where the buffer gets filled with index leaving only little space for data pages. This will result in high disk read percentage when data is accessed. This behaviour is known as PTS defect 121515 CUSTOMERS WITH LOTS OF WIDE INDEXES CAN SEE SEVERE PERFORMANCE PROBLEMS BECAUSE OVER 90% OF THE BUFFER POOL IS FILLED WITH INDEX BRANCH NODES In 7.31 there is an undocumented environment variable LRUAGE , which have to be set before IDS gets started. In SAP environment this is default, as this bug usually affects large OLTP systems. Set it to 1 in the environment of the user who starts IDS server. This will lead to the effect that buffer priorities will get downgraded regularly for all types of pages. Also, I recommend to consider an upgrade to a later 7.31 version (maybe 7.31.UD6 or UD7 ) , as 7.31.UC2 is rather outdated meanwhile. With kind regards Tilman Model-Bosch -- Tilman Model-Bosch IBM Data Managment Solutions, Informix Advanced Support c\\\\o SAP AG TECHDEV 05 Neurrotstr.16 69190 Walldorf "miyaki " <lcib@yahoo.com> To: ids@iiug.org Sent by: cc: forum.subscriber@ Subject: how to tune buffer allocated to index data? [2661] iiug.org 03/12/2004 04:56 AM Hi all, I noticed that the buffer allocated to the index data was extremely high in my database (version 7.31.UC2). May I know which parameter (in onconfig) manage this buffer and how to tune it? Percentages: Data 12.16 Btree 86.52 Other 1.32 TIA, Miyaki __________________________________ Do you Yahoo!? Yahoo! Search - Find what you’re looking for faster http://search.yahoo.com