RE: Analyzing indexes
Title: RE: Analyzing indexes Chuck, Do you think these indexes are corrupt? Validate structure doesn't give you statistics like Compute Statistics or Estimate Statistics does. Jerry Whittle ASIFICS DBA NCI Information Systems Inc. [EMAIL PROTECTED] 618-622-4145 -Original Message- From: Chuck Hamilton [SMTP:[EMAIL PROTECTED] I need to determine whether or not a couple of indexes need to be rebuilt. The problem is the indexes are quite large and on a 24x7 high volume database. If I try to run an analyze validate structure to gather the data I need to make that decision, it sets a lock on the table for about an hour which I can't afford to do. There is no slow time when I can do this and management has said before they're not going to spring for the partitioning option to break the indexes up into managable pieces. Is there some other way I can get the information needed to determine if an index needs to be rebuilt or not without setting a lock on the table? We are on Oracle 8.1.7.
Re: Analyzing indexes
RE: Analyzing indexesNo but validate structure populates the index_stats view which is the only way I know of to get the index height, leaf rows, deleted leaf rows, and pct. of used space which is what I normally use in determining if an index needs to be rebuilt or not. Is there another way? - Original Message - To: Multiple recipients of list ORACLE-L Sent: Tuesday, March 11, 2003 10:49 AM Chuck, Do you think these indexes are corrupt? Validate structure doesn't give you statistics like Compute Statistics or Estimate Statistics does. Jerry Whittle ASIFICS DBA NCI Information Systems Inc. [EMAIL PROTECTED] 618-622-4145 -Original Message- I need to determine whether or not a couple of indexes need to be rebuilt. The problem is the indexes are quite large and on a 24x7 high volume database. If I try to run an analyze validate structure to gather the data I need to make that decision, it sets a lock on the table for about an hour which I can't afford to do. There is no slow time when I can do this and management has said before they're not going to spring for the partitioning option to break the indexes up into managable pieces. Is there some other way I can get the information needed to determine if an index needs to be rebuilt or not without setting a lock on the table? We are on Oracle 8.1.7. -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Chuck Hamilton INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
Re: Analyzing indexes
Chuck, I've been convinced that rebuilding indexes is a waste of time. In fact, it can cost you time, as rebuilding indexes can kill your peformance while the indexes again seek their 'level'. Check into at asktom.oracle.com. There's some good examples. jared Chuck Hamilton [EMAIL PROTECTED] Sent by: [EMAIL PROTECTED] 03/11/2003 06:30 AM Please respond to ORACLE-L To: Multiple recipients of list ORACLE-L [EMAIL PROTECTED] cc: Subject:Analyzing indexes I need to determine whether or not a couple of indexes need to be rebuilt. The problem is the indexes are quite large and on a 24x7 high volume database. If I try to run an analyze validate structure to gather the data I need to make that decision, it sets a lock on the table for about an hour which I can't afford to do. There is no slow time when I can do this and management has said before they're not going to spring for the partitioning option to break the indexes up into managable pieces. Is there some other way I can get the information needed to determine if an index needs to be rebuilt or not without setting a lock on the table? We are on Oracle 8.1.7. -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Chuck Hamilton INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
RE: Analyzing indexes
Chuck I think Jared has some excellent advice (as usual). Interestingly, while you may need to lock the table while analyzing the table, you may be able to rebuild it without locking it. According to the Oracle Education notes, Oracle8i introduced a method of re-creating and existing index while allowing concurrent operations on the base table. The syntax is ALTER INDEX xxx REBUILD ONLINE; or ALTER INDEX xxx COALESCE; If you really feel you must do something, the coalesce may be a lower-risk solution. It won't lower the height, but as Jared points out, that may be of only temporary value. Either way, I'd try it in test first. Dennis Williams DBA, 40%OCP, 100% DBA Lifetouch, Inc. [EMAIL PROTECTED] -Original Message- Sent: Tuesday, March 11, 2003 1:04 PM To: Multiple recipients of list ORACLE-L Chuck, I've been convinced that rebuilding indexes is a waste of time. In fact, it can cost you time, as rebuilding indexes can kill your peformance while the indexes again seek their 'level'. Check into at asktom.oracle.com. There's some good examples. jared Chuck Hamilton [EMAIL PROTECTED] Sent by: [EMAIL PROTECTED] 03/11/2003 06:30 AM Please respond to ORACLE-L To: Multiple recipients of list ORACLE-L [EMAIL PROTECTED] cc: Subject:Analyzing indexes I need to determine whether or not a couple of indexes need to be rebuilt. The problem is the indexes are quite large and on a 24x7 high volume database. If I try to run an analyze validate structure to gather the data I need to make that decision, it sets a lock on the table for about an hour which I can't afford to do. There is no slow time when I can do this and management has said before they're not going to spring for the partitioning option to break the indexes up into managable pieces. Is there some other way I can get the information needed to determine if an index needs to be rebuilt or not without setting a lock on the table? We are on Oracle 8.1.7. -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Chuck Hamilton INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: DENNIS WILLIAMS INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
Re: Analyzing indexes
If you want the index height (or blevel + 1), then you could dump the index root block alter system dump datafile N block MM Check dba_segments for the address of the segment header block, unless you have multiple freelist groups, the index root block will be the one after the segment header. You will find the blevel of the root block in the symbolic dump in the line labelled kdxcolev. For the 'right size' - I tend to work out roughly how large a typical index entry ought to be, multiple by the number of rows I expect to have non-null entries - add a bit (for rowids) and multiple by 4/3 (to allow for typical wastage). If the result is about right, I stop worrying. (NB There may be special case indexes where you have a finer knowledge of the application and therefore use a value other than 4/3). Regards Jonathan Lewis http://www.jlcomp.demon.co.uk Now available One-day tutorials: Cost Based Optimisation Trouble-shooting and Tuning Indexing Strategies (see http://www.jlcomp.demon.co.uk/tutorial.html ) UK___March 19th UK___April 8th UK___April 22nd USA_(FL)_May 2nd Next dates for the 3-day seminar: (see http://www.jlcomp.demon.co.uk/seminar.html ) UK_(Manchester)_May USA_(CA, TX)_August The Co-operative Oracle Users' FAQ http://www.jlcomp.demon.co.uk/faq/ind_faq.html - Original Message - To: Multiple recipients of list ORACLE-L [EMAIL PROTECTED] Sent: 11 March 2003 14:30 I need to determine whether or not a couple of indexes need to be rebuilt. The problem is the indexes are quite large and on a 24x7 high volume database. If I try to run an analyze validate structure to gather the data I need to make that decision, it sets a lock on the table for about an hour which I can't afford to do. There is no slow time when I can do this and management has said before they're not going to spring for the partitioning option to break the indexes up into managable pieces. Is there some other way I can get the information needed to determine if an index needs to be rebuilt or not without setting a lock on the table? We are on Oracle 8.1.7. -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Jonathan Lewis INET: [EMAIL PROTECTED] Fat City Network Services-- 858-538-5051 http://www.fatcity.com San Diego, California-- Mailing list and web hosting services - To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
