oracle statspack实例(一)

大 db_block_size; 大; db_cache_size使用多个块大小多个数据库写入(DBWR)进程大sort_area_size大的在线重作日志Oracle; 对象在数据库内部(表和索引的设置可以减少物理磁盘IO)低pctused; pctuseed的值越小,随后的sql插入中出现的io就越少低pctfree 假如设置了pctfree,以答应在没有分割的情况下扩展所有行,那么在随后的sql选择中就会产生更少的磁盘io使用索引将表重新组织成簇行; 假如以最常使用索引的相同物理次序放置表3 oracle; sql 在sql语句内,有许多技术可以减少物理磁盘io使用索引或提示(hint)防止不必要的全表搜索使用位映射(bitmapped)索引应用sql提示oracle; 内部结构和磁盘io;--查找稀疏表(自由表失去平衡!)select substr(dt.table_name,1,10) c3,ds.extentsc5,ds.bytes/1048576;c4,dt.next_extent/1048576; c8,(dt.empty_blocks*4096)/1048576 c7,(ds.bytes*4096)/1048576;;c6,(avg_row_len*num_rows)/(db.blocks*4096) c10from sys.dba_segments; ds , sys.dba_tables;dtwhere --调整oracle数据库实例接下来我们要调整oracle数据库实例,以及查看所有影响性能的 参数,配置和设定用STATAPACK检测实例潜在的性能问题1.oracle实例概述2.调整oracle 数据缓冲区3.调整共享池概述4.调整库高速缓存5.调整oracle排序6.调整回滚段7.oracle 9i RAM 内存调整通常的角度看; oracle实例包括了两个组件:; 系统全局区(SGA) 以及 oracle后台进程我们通常通过调整oracle参数来控制SGA和后台进程当oracle启动时 oracle就会使用malloc()命令去建立一个RAM内存区域,这个SGA通常也称为oracle区域oracle DBA 可以控制SGA的规模; 正确的SGA治理可以极大的影响性能尽管初始化参数成百上千但是只有很少的oracle9i参数对调整非常重要:buffer_pool_keep这个数据缓冲池用于存储执行全表扫描的小表buffer_pool_recycle这个池用来保存进行全表扫描的非常大的表的表块db_cache_size;这个参数会决定ORACLE; SGA; 中数据库块缓冲区的数量,它是oracle内存的最重要的参数db_block_size 数据库块大小能够对性能产生(作为一个一般的规则,块尺寸越大,物理IO就越少,整体性能就越快)db_file_multiblock_read_count; 这个参数用于全表搜索或者大表范围扫描的时候,进行多块读入large_pool_szie 这是一个使用多线程服务器的时候,保留用于SGA使用的共享池中的非凡区域.最大池也用于并行查询RAM进程log_buffer这个参数会决定为oracle重作日志缓冲区分配的内存数量.假如具有大量的更新活动，就应该给log_buffer分配更多的空间shared_pool_size这个参数会定义系统中所有用户的共享池,包括SQL区域和数据字典高速缓存.--有三个oracle参数可以影响数据缓冲区的大小db_cache_sizebuffer_pool_keepbuffer_pool_recycleoracle建议缓冲区的命中率要超过90％ DBA可以通过给初始化参数增加数据块数量来控制数据缓冲区命中率数据库缓冲池的内部结构--使用statspack监视缓冲池的使用--缓冲池命中率和statpackselect * from stats$buffer_pool_statisticsSGA_MAX_SIZE=6000MDB_BLOCK_SIZE=16384DB_CACHE_SIZE=5000MBUFFER_POOL_KEEP=(1400,3)BUFFER_POOL_RECYCLE=(900,3)--在oracle8; 可以使用ALTER; TABLE CUSTOMER; STORAGE(buffer_pool; KEEP); ALTER TABLE USER.TABLE_NAME;STORAGE(buffer_pool; keep);--高级KEEP池候选识别除了进行全表扫描的小表之外，keep缓冲池还非常适合放置频繁使用的数据段的数据块--使用x$bh视图来识别平均块接触次数超过5次，并且在缓存中占用超过20个数据块的对象--hot_buffer.sql--识别热点对象;select object_typemytype,object_name;myname ,blocks,count(1) buffers,avg(tch) avg_toUChesfromsys.x$bh a,dba_objects; b,dba_segments swhere a.obj=b.object_idand b.object_name=s.segment_nameand b.owner; not in('SYS','SYSTEM')GROUP BY object_name,object_type,blocks,objhaving; avg(tch)>5and count(1)>20;识别出热点对象后，可以决定将对象隔离放入keep池中作为一般的规则，应该有足够的RAM存储可以用于整个表或者索引列如，假如希望为keep池增加页表，就需要给init.ora的buffer_pool_keep; 参数增加104个数据块--调整 recycle 池在recycle池放置对象的目标是将全表搜索频率的大表进行分离，为了找到进行全表搜索的大表，我们必须求助于从Access.sql中获得的全表搜索报告：access_recycle_syntax.sqlselect 'alter table 'p.owner'.'p.name' storage (buffer_pool; recyle);'from dba_tables t,dba_segments s,sqltemp s,(select distinct statement_id; stid, object_owner; owner, object_namenamefrom plan_table where operation='TABLE ACCESS' and options='FULL') pwhere s.addr':'TO_CHAR(s.hashval)=p.stidand t.table_name=p.nameand t.owner=p.ownerand t.buffer_pool<>'RECYCLE'having; s.blocks>1000group by p.owner,p.name,t.num_rows,s.blocksorder by sum(s.executions) desc;--给表分配recycle池altertableuser.table_name storage(buffer_pool; recycle);注重：在将任何表加入到RECYCLE池之前，DBA都应该抽取sql源代码，并且验证这个查询是否获取超过了表中行的40％--高级recycle池调整下列查询使用了x$bh.tch来识别具有一次缓冲区接触计数，但是总量超过了整个缓存的5％的数据缓存中的对象，这些数据段是潜在的在recycle缓冲池中放置的候选对象，因为他们可能会让不会重用的数据块占用大量的缓存空间select object_type; mytype,object_name; myname,blocks,count(1) buffers,100*(count(1)/totsize); pct_cachefrom sys.x$bha,dba_objects b,dba_segments s,()--取消跟踪功能alter system set trace_enabled=false;--STATISTICS_LEVELThe STATISTICS_LEVEL parameter was introduced in Oracle9i Release 2 (9.2) to control all major statistics collections or advisories in the database. The level of the setting affects the number of statistics and advisories that are enabled:BASIC: No advisories or statistics are collected.TYPICAL: The following advisories or statistics are collected:Buffer cache advisory MTTR advisory Shared Pool sizing advisory Segment level statistics PGA target advisory Timed statistics ALL: All of TYPICAL, plus the following: Timed operating system statistics Row source execution statistics The parameter is dynamic and can be altered using:ALTER SYSTEM SET statistics_level=basic;ALTER SYSTEM SET statistics_level=typical;ALTER SYSTEM SET statistics_level=all;Current settings for parameters can be shown using:SHOW PARAMETER statistics_levelSHOW PARAMETER timed_statisticsOracle can only manage statistic collections and advisories whose parameter setting is undefined in the spfile. By default the TIMED_STATISTICS parameter is set to TRUE so this must be reset for it to be controled by the statistics level, along with any other conflicting parameters:ALTER SYSTEM RESET timed_statistics scope=spfile sid='*';This setting will not take effect until the database is restarted.At this point the affect of the statistics level can be shown using the following query:COLUMN statistics_name;;;FORMAT A30 HEADING 'Statistics Name'COLUMN session_status;;;;FORMAT A10 HEADING 'SessionStatus'COLUMN system_status;;;;;FORMAT A10 HEADING 'SystemStatus'COLUMN activation_level;;FORMAT A10 HEADING 'ActivationLevel'COLUMN session_settable;;FORMAT A10 HEADING 'SessionSettable'SELECT statistics_name, session_status, system_status, activation_level, session_settableFROMv$statistics_levelORDER BY statistics_name;A comparison between the levels can be shown as follows:SQL> ALTER SYSTEM SET statistics_level=basic;System altered.SQL> SELECT statistics_name, 2 session_status, 3 system_status, 4 activation_level, 5 session_settable 6; FROMv$statistics_level 7; ORDER BY statistics_name;;;;;Session;System;;Activation SessionStatistics Name;;;;;Status;;Status;;Level;;;Settable------------------------------ ---------- ---------- ---------- ---------- Buffer Cache Advice;DISABLEDDISABLEDTYPICAL;NOMTTR Advice;DISABLEDDISABLEDTYPICAL;NOPGA Advice;;DISABLEDDISABLEDTYPICAL;NOPlan Execution Statistics;;;DISABLEDDISABLEDALL;;;;;YESSegment Level Statistics;;;;DISABLEDDISABLEDTYPICAL;NOShared Pool Advice;;DISABLEDDISABLEDTYPICAL;NOTimed OS Statistics;DISABLEDDISABLEDALL;;;;;YESTimed Statistics;;;;DISABLEDDISABLEDTYPICAL;YES8 rows selected.SQL> ALTER SYSTEM SET statistics_level=typical;System altered.SQL> SELECT statistics_name, 2 session_status, 3 system_status, 4 activation_level, 5 session_settable 6; FROMv$statistics_level 7; ORDER BY statistics_name;;;;;Session;System;;Activation SessionStatistics Name;;;;;Status;;Status;;Level;;;Settable------------------------------ ---------- ---------- ---------- ----------Buffer Cache Advice;ENABLED;ENABLED;TYPICAL;NOMTTR Advice;ENABLED;ENABLED;TYPICAL;NOPGA Advice;;ENABLED;ENABLED;TYPICAL;NO Plan Execution Statistics;;;DISABLEDDISABLEDALL;;;;;YESSegment Level Statistics;;;;ENABLED;ENABLED;TYPICAL;NOShared Pool Advice;;ENABLED;ENABLED;TYPICAL;NOTimed OS Statistics;DISABLEDDISABLEDALL;;;;;YESTimed Statistics;;;;ENABLED;ENABLED;TYPICAL;YES8 rows selected.SQL> ALTER SYSTEM SET statistics_level=all;System altered.SQL> SELECT statistics_name, 2 session_status, 3 system_status, 4 activation_level, 5 session_settable 6; FROMv$statistics_level 7; ORDER BY statistics_name;;;;;Session;System;;Activation SessionStatistics Name;;;;;Status;;Status;;Level;;;Settable------------------------------ ---------- ---------- ---------- ----------Buffer Cache Advice;ENABLED;ENABLED;TYPICAL;NOMTTR Advice;ENABLED;ENABLED;TYPICAL;NOPGA Advice;;ENABLED;ENABLED;TYPICAL;NOPlan Execution Statistics;;;ENABLED;ENABLED;ALL;;;;;YESSegment Level Statistics;;;;ENABLED;ENABLED;TYPICAL;NOShared Pool Advice;;ENABLED;ENABLED;TYPICAL;NO Timed OS Statistics;ENABLED;ENABLED;ALL;;;;;YESTimed Statistics;;;;ENABLED;ENABLED;TYPICAL;YES8 rows selected.SQL>Hope this helps. Regards Tim...