Re: confused about # of extents per segment performance issue
Besides DDL like tuncate and drop will take longer with large # of extents Regards Rafiq Reply-To: [EMAIL PROTECTED] To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]> Date: Tue, 27 Feb 2001 10:31:24 -0800 This really depends on the type of access. If it's random using indexes, the extents don't matter much. If you do a lot of full table scans, and the extents are scattered all over, there may be a performance degradation. YMMV as always. >>> [EMAIL PROTECTED] 02/27/01 01:06PM >>> Apparently, it's a widely held myth that a large # of extents (let's say "BETWEEN 5 AND 1000") per table segment is bad for performance. Yet the same sources who label the belief mistaken persist in pushing for fitting all of a table in the INITIAL extent. And that confuses the heck out of me. What gives? Is it that fetching a new extent on the fly, the act of obtaining a new extent, creates too much overhead? And finis, no more concern beyond this? If you approached a database for the first time and it already contained a segment with 500 extents, would that segment's number of extents not be a performance concern unless you expected it to continue grabbing new extents? Let's say it would never have a new insert, update, or delete. Would there be any performance value in crushing the segment down to fit in one extent? What's the definitive answer on this? I remain confused about coalescing as well; anyone know of a good whitepaper or article on coalescing/fragmentation for Oracle 8 and beyond? Thanks. - Dana __ Do You Yahoo!? Get email at your own domain with Yahoo! Mail. http://personal.mail.yahoo.com/ -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: dana mn 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: Tim Sawmiller 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). _ Get your FREE download of MSN Explorer at http://explorer.msn.com -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Mohammad Rafiq 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: confused about # of extents per segment performance issue
This really depends on the type of access. If it's random using indexes, the extents don't matter much. If you do a lot of full table scans, and the extents are scattered all over, there may be a performance degradation. YMMV as always. >>> [EMAIL PROTECTED] 02/27/01 01:06PM >>> Apparently, it's a widely held myth that a large # of extents (let's say "BETWEEN 5 AND 1000") per table segment is bad for performance. Yet the same sources who label the belief mistaken persist in pushing for fitting all of a table in the INITIAL extent. And that confuses the heck out of me. What gives? Is it that fetching a new extent on the fly, the act of obtaining a new extent, creates too much overhead? And finis, no more concern beyond this? If you approached a database for the first time and it already contained a segment with 500 extents, would that segment's number of extents not be a performance concern unless you expected it to continue grabbing new extents? Let's say it would never have a new insert, update, or delete. Would there be any performance value in crushing the segment down to fit in one extent? What's the definitive answer on this? I remain confused about coalescing as well; anyone know of a good whitepaper or article on coalescing/fragmentation for Oracle 8 and beyond? Thanks. - Dana __ Do You Yahoo!? Get email at your own domain with Yahoo! Mail. http://personal.mail.yahoo.com/ -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: dana mn 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: Tim Sawmiller 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).
confused about # of extents per segment performance issue
Apparently, it's a widely held myth that a large # of extents (let's say "BETWEEN 5 AND 1000") per table segment is bad for performance. Yet the same sources who label the belief mistaken persist in pushing for fitting all of a table in the INITIAL extent. And that confuses the heck out of me. What gives? Is it that fetching a new extent on the fly, the act of obtaining a new extent, creates too much overhead? And finis, no more concern beyond this? If you approached a database for the first time and it already contained a segment with 500 extents, would that segment's number of extents not be a performance concern unless you expected it to continue grabbing new extents? Let's say it would never have a new insert, update, or delete. Would there be any performance value in crushing the segment down to fit in one extent? What's the definitive answer on this? I remain confused about coalescing as well; anyone know of a good whitepaper or article on coalescing/fragmentation for Oracle 8 and beyond? Thanks. - Dana __ Do You Yahoo!? Get email at your own domain with Yahoo! Mail. http://personal.mail.yahoo.com/ -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: dana mn 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).