For a given statements execution, running in serial, you will not find an index and a table being accessed in parallel. Thus, there is no contention, for a given statement, between the tables and indexes accessed by that statement. Thus, one could argue the merits of not needing to seperate indexes and data in a low concurrency environment.
OTOH, high concurrency leads to hot blocks, which often leads to a requirement of distributing IO. In this case, seperating indexes and data may be one step in that direction. RAID technologies, if properly configured, can eliminate some of the risk from co-location of data of course.... but in the end there is no substitute for carefully laid out data. RF -----Original Message----- To: Multiple recipients of list ORACLE-L Sent: 7/15/2003 10:29 AM datafiles does anyoen disagree? Didnt this get started with the 'DBA Handbook' or was it a different text? > > From: "Mercadante, Thomas F" <[EMAIL PROTECTED]> > Date: 2003/07/15 Tue AM 11:10:05 EDT > To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]> > Subject: RE: should you seperate indexes from tables in seperate datafiles > > R, > > Some of it depends on the disk storage. I have always followed the > time-proven method of organizing disks and placing indexes away from the > tables they belong to. > > Our warehouse is using EMC external disk. What the warehouse architect did > was to stripe the EMC disks in such a way that all mount points (Sun system) > are spread across all the EMC disks. What this does is to spread all files > in the database across all the EMC drives. And with 4 Gig of EMC cache > available, it further disproves the theory that separing indexes from data > are required. The end result, in my case, is almost like one big RAM disk - > where all disk IO is spread across all disk. > > If you do not have this arrangement, then I would still try and keep indexes > and data away from each other. But let's face it, we *never* have enough > disk mount points, so we end up merging things together somewhat anyway. > > hope this helps. > > Tom Mercadante > Oracle Certified Professional > > > -----Original Message----- > Sent: Tuesday, July 15, 2003 10:49 AM > To: Multiple recipients of list ORACLE-L > > > There has been alot of literature stating that you will recieve performance > improvements by seperating indexes and tables across multiple I/O points. > > Ie... you have a tables tablespace and an index tablespace. If you put them > on seperate hard drives, you will have less I/O contention. > > Now Im seeing some articles stating that this is not true. That oracle > actually accesses indexes and tables serially. Now it might be useful > seperate indexes from tables for maintenance purposes but this wont lower > I/O contention. > > Can anyone chime in on this? Curious to see where the evidence is leading? > > -- > Please see the official ORACLE-L FAQ: http://www.orafaq.net > -- > Author: <[EMAIL PROTECTED] > 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: Mercadante, Thomas F > 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: <[EMAIL PROTECTED] 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: Freeman Robert - IL 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).
