Re:RE: Extents size.
Back in the V6 days it was a desired characteristic to have every thing in the first extent of an object for performance reasons. Thankfully those days are gone and it really does not matter how many extents there are. Rachel has a presentation on Oracle Myths where she actually portrays having multiple extents as a good thing from an IO perspective (Rachel, correct me if I got this wrong). Although I can't give you exact examples, take a look and v$filestat. I've found that tablespaces where there are more than one extent in the objects have a lower average io wait time that those where everything is in the first extent. The only real good reason I have found for re-organizing a tablespace is to get all of the used extents at one end and all of the free extents (you know those little bitty ones that individually aren't worth the trouble, but together!!) at the other end. Dick Goulet Reply Separator Author: Christopher Spence [EMAIL PROTECTED] Date: 10/2/2001 7:55 AM That is completely a myth. There is no notable performance different with a table with 10,000 extents and one with 1. The only problem is when it comes to the bitmaps when dealing with LMT and cluster when dealing with dictionary managed. When you query the extent views, or do space management type processes. Do not criticize someone until you walked a mile in their shoes, that way when you criticize them, you are a mile a way and have their shoes. Christopher R. Spence Oracle DBA Phone: (978) 322-5744 Fax:(707) 885-2275 Fuelspot 73 Princeton Street North, Chelmsford 01863 -Original Message- Sent: Monday, October 01, 2001 7:15 PM To: Multiple recipients of list ORACLE-L May be it is good practice to keep number of extents to be less than 50, no matter what the size of extent. -Original Message- Sent: Monday, October 01, 2001 3:35 PM To: Multiple recipients of list ORACLE-L Hello, I'll do an reorganization of a database (about 140 gigs). Some people say that it'd be good to use 128K, 4M and 128M extents. I saw somewhere it'd be 160K, 4M and 160M. Which size do you advice me ? I have also many small indexes (less than 16K). Regards, Thanh-truc Nguyen -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Thanh-truc Nguyen INET: [EMAIL PROTECTED] Fat City Network Services-- (858) 538-5051 FAX: (858) 538-5051 San Diego, California-- Public Internet access / Mailing Lists 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.com -- Author: Wong, Bing INET: [EMAIL PROTECTED] Fat City Network Services-- (858) 538-5051 FAX: (858) 538-5051 San Diego, California-- Public Internet access / Mailing Lists 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.com -- Author: Christopher Spence INET: [EMAIL PROTECTED] Fat City Network Services-- (858) 538-5051 FAX: (858) 538-5051 San Diego, California-- Public Internet access / Mailing Lists 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.com -- Author: INET: [EMAIL PROTECTED] Fat City Network Services-- (858) 538-5051 FAX: (858) 538-5051 San Diego, California-- Public Internet access / Mailing Lists 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:RE: Extents size.
something along those lines... as with everything there is no real black or white on this... but transactional systems that do a lot of small (non-sequential) reads you are better off with lots of extents while data warehouses are often better off with fewer extents as the reads tend to be sequential or full table scans so you would want more of the data together as for those little bitty extents -- you mean you aren't using tablespaces with a single extent size so you don't have to worry about them? --- [EMAIL PROTECTED] wrote: Back in the V6 days it was a desired characteristic to have every thing in the first extent of an object for performance reasons. Thankfully those days are gone and it really does not matter how many extents there are. Rachel has a presentation on Oracle Myths where she actually portrays having multiple extents as a good thing from an IO perspective (Rachel, correct me if I got this wrong). Although I can't give you exact examples, take a look and v$filestat. I've found that tablespaces where there are more than one extent in the objects have a lower average io wait time that those where everything is in the first extent. The only real good reason I have found for re-organizing a tablespace is to get all of the used extents at one end and all of the free extents (you know those little bitty ones that individually aren't worth the trouble, but together!!) at the other end. Dick Goulet Reply Separator Author: Christopher Spence [EMAIL PROTECTED] Date: 10/2/2001 7:55 AM That is completely a myth. There is no notable performance different with a table with 10,000 extents and one with 1. The only problem is when it comes to the bitmaps when dealing with LMT and cluster when dealing with dictionary managed. When you query the extent views, or do space management type processes. Do not criticize someone until you walked a mile in their shoes, that way when you criticize them, you are a mile a way and have their shoes. Christopher R. Spence Oracle DBA Phone: (978) 322-5744 Fax:(707) 885-2275 Fuelspot 73 Princeton Street North, Chelmsford 01863 -Original Message- Sent: Monday, October 01, 2001 7:15 PM To: Multiple recipients of list ORACLE-L May be it is good practice to keep number of extents to be less than 50, no matter what the size of extent. -Original Message- Sent: Monday, October 01, 2001 3:35 PM To: Multiple recipients of list ORACLE-L Hello, I'll do an reorganization of a database (about 140 gigs). Some people say that it'd be good to use 128K, 4M and 128M extents. I saw somewhere it'd be 160K, 4M and 160M. Which size do you advice me ? I have also many small indexes (less than 16K). Regards, Thanh-truc Nguyen -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Thanh-truc Nguyen INET: [EMAIL PROTECTED] Fat City Network Services-- (858) 538-5051 FAX: (858) 538-5051 San Diego, California-- Public Internet access / Mailing Lists 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.com -- Author: Wong, Bing INET: [EMAIL PROTECTED] Fat City Network Services-- (858) 538-5051 FAX: (858) 538-5051 San Diego, California-- Public Internet access / Mailing Lists 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.com -- Author: Christopher Spence INET: [EMAIL PROTECTED] Fat City Network Services-- (858) 538-5051 FAX: (858) 538-5051 San Diego, California-- Public Internet access / Mailing Lists 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.com -- Author: INET: [EMAIL PROTECTED] Fat City
Re:RE: Extents size.
I would content that the moment the extent size is greater than SSTIOMAX (or whatever the OS can service), then you won't see any benefit from fewer extents even on data warehouse - the only exception I can think is if you were lucky enough to be the only user on a particular disk/volume during the run of your query - which I think would be extremely rare. This is not to say that reorgs are not worthwhile - I've seen warehouses triple in performance simply by pseudo-clustering the data during reload to get some affinity with the typical queries run against it. To respond to the previous post - locally managed tablespaces are a wonderful way of migrating all your segments down to the front of a tablespace - it just happens automagically with an alter table move hth connor --- Rachel Carmichael [EMAIL PROTECTED] wrote: something along those lines... as with everything there is no real black or white on this... but transactional systems that do a lot of small (non-sequential) reads you are better off with lots of extents while data warehouses are often better off with fewer extents as the reads tend to be sequential or full table scans so you would want more of the data together as for those little bitty extents -- you mean you aren't using tablespaces with a single extent size so you don't have to worry about them? --- [EMAIL PROTECTED] wrote: Back in the V6 days it was a desired characteristic to have every thing in the first extent of an object for performance reasons. Thankfully those days are gone and it really does not matter how many extents there are. Rachel has a presentation on Oracle Myths where she actually portrays having multiple extents as a good thing from an IO perspective (Rachel, correct me if I got this wrong). Although I can't give you exact examples, take a look and v$filestat. I've found that tablespaces where there are more than one extent in the objects have a lower average io wait time that those where everything is in the first extent. The only real good reason I have found for re-organizing a tablespace is to get all of the used extents at one end and all of the free extents (you know those little bitty ones that individually aren't worth the trouble, but together!!) at the other end. Dick Goulet Reply Separator Author: Christopher Spence [EMAIL PROTECTED] Date: 10/2/2001 7:55 AM That is completely a myth. There is no notable performance different with a table with 10,000 extents and one with 1. The only problem is when it comes to the bitmaps when dealing with LMT and cluster when dealing with dictionary managed. When you query the extent views, or do space management type processes. Do not criticize someone until you walked a mile in their shoes, that way when you criticize them, you are a mile a way and have their shoes. Christopher R. Spence Oracle DBA Phone: (978) 322-5744 Fax:(707) 885-2275 Fuelspot 73 Princeton Street North, Chelmsford 01863 -Original Message- Sent: Monday, October 01, 2001 7:15 PM To: Multiple recipients of list ORACLE-L May be it is good practice to keep number of extents to be less than 50, no matter what the size of extent. -Original Message- Sent: Monday, October 01, 2001 3:35 PM To: Multiple recipients of list ORACLE-L Hello, I'll do an reorganization of a database (about 140 gigs). Some people say that it'd be good to use 128K, 4M and 128M extents. I saw somewhere it'd be 160K, 4M and 160M. Which size do you advice me ? I have also many small indexes (less than 16K). Regards, Thanh-truc Nguyen -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Thanh-truc Nguyen INET: [EMAIL PROTECTED] Fat City Network Services-- (858) 538-5051 FAX: (858) 538-5051 San Diego, California-- Public Internet access / Mailing Lists 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.com -- Author: Wong, Bing INET: [EMAIL PROTECTED] Fat City Network Services-- (858) 538-5051 FAX: (858) 538-5051 San Diego, California-- Public Internet access / Mailing Lists To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of
