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  1. 1. Script:Speed Up Large Index Create or Rebuild by Maclean.liu
  2. 2. About Mel Email:liu.maclean@gmail.coml Blog:www.oracledatabase12g.coml Oracle Certified Database Administrator Master 10gand 11gl Over 6 years experience with Oracle DBA technologyl Over 7 years experience with Linux technologyl Member Independent Oracle Users Groupl Member All China Users Groupl Presents for advanced Oracle topics: RAC,DataGuard, Performance Tuning and Oracle Internal.
  3. 3. 简单测试过,创建 25g 大小的索引,普通 pc 机不做任何优化大约要 1 个小时,优化后 35 分钟完成。因为之前经常有业务人员问我怎么加速索引创建或重建,所以萌发了把能优化的选项集中在一个脚本里的想法,但也仅是指导思想(绝大多数场景应当是有效的)。以上主要优化的几点:1.普通多块读和排序多块读的大小2.直接路径 IO 的大小,10351 event level 1283.内存排序空间的大小,10g 中存在 bug 需要 2 次设置。在 10g 中针对 parallel execution 环境也需要设置_sort_multiblock_read_count。但是仅对能从内存获益的排序操作有利,适合大多数场景4.nologging5.并行,一般这个业务人员也会想到6.独立的临时表空间7.使用备选的排序算法_newsort_type 或_newsort_enabled,一般不要用8.禁用 block checksum/checking,不推荐,尽在新系统加载大量数据时使用以下脚本可以用于加速大表索引的创建或重建SQL> select * from v$version;BANNER--------------------------------------------------------------------------------Oracle Database 11g Enterprise Edition Release - 64bit ProductionPL/SQL Release - ProductionCORE ProductionTNS for Linux: Version - ProductionNLSRTL Version - ProductionSQL> select * from global_name;GLOBAL_NAME--------------------------------------------------------------------------------
  4. 4. Script Tested above 10g-- Create a new temporary segment tablespace specifically for creating theindex.-- CREATE TEMPORARY TABLESPACE tempindex tempfile filename SIZE 20G ;-- ALTER USER username TEMPORARY TABLESPACE tempindex;REM PARALLEL_EXECUTION_MESSAGE_SIZE can be increased to improve throughput.REM but need restart instance,and should be same in RAC environmentREM this doesnt make sense,unless high parallel degree-- alter system set parallel_execution_message_size=65535 scope=spfile;alter session set workarea_size_policy=MANUAL;alter session set workarea_size_policy=MANUAL;alter session set db_file_multiblock_read_count=512;alter session set db_file_multiblock_read_count=512;--In conclusion, in order to have the least amount of direct operations and--have the maximum possible read/write batches these are the parameters to set:alter session set events 10351 trace name context forever, level 128;REM set sort_area_size to 700M or 1.6 * table_sizeREM 10g bug need to set sort_area_size twiceREM remember large sort area size doesnt mean better performanceREM sometimes you should reduce below setting,and then sort may benefit fromdisk sortREM and attention to avoid PGA swapalter session set sort_area_size=734003200;alter session set sort_area_size=734003200;REM set sort area first,and then set SMRC for parallel slaveREM Setting this parameter can activate our previous setting of sort_area_sizeREM and we can have large sort multiblock read counts.alter session set "_sort_multiblock_read_count"=128;alter session set "_sort_multiblock_read_count"=128;alter session enable parallel ddl;create [UNIQUE] index ... [ONLINE] parallel [Np] nologging;alter index .. logging;alter index .. noparallel;--TRY below underscore parameter while poor performance--alter session set "_shrunk_aggs_disable_threshold"=100;REM _newsort_type=2 only works if the patch for bug:4655998 has been appliedREM The fix for bug:4655998 has been included in the patchset.REM got worse in most cases--alter session set "_newsort_type" = 2;OR--alter session set "_newsort_enabled"=false; then useSort V1 algorithm,got worse in most casesrem !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!IMPORTANT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
  5. 5. rem If the performance of a query has degraded and the majority of therem time is spent in the function kghfrempty, and the function that calledrem kghfrempty was kxsfwa called from kksumc, then you may be encounteringrem this problem.rem Workaround:rem Reducing sort_area_size may help by reducing the amount of memory thatrem each sort allocates, particularly if the IO subsystem is underutilized.rem The performance of some queries that involved large sorts degraded duerem to the memory allocation pattern used by sort.rem !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!REM setting below parameter only if you are loading data into new systemREM you should restore them after loading--alter session set db_block_checking=false;--alter system set db_block_checksum=false;© 2011, 版权所有.文章允许转载,但必须以链接方式注明源地址,否则追求法律责任.