Thinking Out Loud

November 18, 2015

Extent Allocation

Filed under: 11g,ASM,oracle,performance — mdinh @ 11:43 pm

Some references on extents dealing with extent trimming, initial extent for parallel load, tablespace fragmentation, etc…

ASM AU Size And LMT AUTOALLOCATE
http://oracle-randolf.blogspot.com/2013/04/asm-au-size-and-lmt-autoallocate.html

Parallel Load: Uniform or AutoAllocate extents?
https://blogs.oracle.com/datawarehousing/entry/parallel_load_uniform_or_autoallocate

Tom Kyte covers this problem in great details in his post Loading and Extents
http://www.oracle.com/technetwork/issue-archive/2007/07-may/o37asktom-101781.html

System Managed Extent Size – 11g Improvements
https://antognini.ch/2009/08/system-managed-extent-size-11g-improvements/

PX and system allocation
https://jonathanlewis.wordpress.com/2012/06/14/px-and-system-allocation/

Initial Extent Size of a Partition Changed to 8MB from 64KB After Upgrade to 11.2.0.2 or Later (Doc ID 1295484.1)

Bug 19912552 : PARTITIONED INDEXES CREATED WITH 8M INITIAL EXTENT WHEN _INDEX_PARTITION_LARGE

Segments of type INDEX PARTITION or INDEX SUBPARTITION will be created with 8M initial extent in version 12.1.0.2, instead of 64K in earlier versions.
Global indexes or indexes on non partitioned tables still have 64K.

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2 Comments »

  1. Why do Rekha and Tom provide examples of UNIFORM 100MB extents for loading 1GB data ? Do they think that we subscribe to the “keep the number of extents to the minimum” school of thought ?

    Comment by Hemant K Chitale — November 25, 2015 @ 8:48 am | Reply

    • Short anwser is yes. Less extents, less scan for FTS and contradicting number of extents do not affect performance. Remeber old school was to create small / large tbs? Autoallocate attempts to fix this.

      Comment by mdinh — November 26, 2015 @ 12:39 pm | Reply


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