ORACLE中的AWR功能
1、ASH和AWR的故事
1.1、关于ASH
用户在Oracle数据库中执行操作时必然要创建相应的连接和会话，其中，所有的当前会话信息都保存在动态性能视图v$session中，通过视图，DBA可以查看用户实际执行的操作，或者当前等待的事件。通常这部分信息是调优过程中的关键信息，不过，一旦连接断开。会话信息就会被同时从V$SESSION及其它相关视图中清除。
10g 版本中，ORACLE又新增加了一个视图V$ACTIVE_SESSION_HISTORY，代表活动会话的历史记录，即使用户操作完成后，断开了连接，其会话的情况也会被记录下来，这项特性就是ASH了。
ASH 每秒钟收集一次当前处于非空闲等待事件的、活动状态的、session的信息，并保存在V$ACTIVE_SESSION_HISTORY视图中，我们知道，动态性能视图其实上是ORACLE自行构造的一堆存在于SGA内存区的虚表，就是说，ASH的数据是保存在内存里的，实际上，ORACLE分配给ASH的空间并不是无限大(更何况ORACLE自身管理的内存空间也不是无限大)，查看ASH可供使用的内存空间，可以通过如下SQL：
SQL> select pool,name,bytes/1024/1024 MB from v$sgastat where name like '%ASH%';
POOL NAME MB
------------ -------------------------- ----------
shared pool ASH buffers 8
shared pool UNDO INFO HASH .005706787
SQL>
直白的讲 ，V$ACTIVE_SESSION_HISTORY中能够记录多少会话信息， 一方面取决于该数据库的SGA 分配给ASH buffers的大小 ，另一方面取决于数据库的启动和关闭(重启数据库时将重构SGA内存区)。这两方面的因素制约了V$ACTIVE_SESSION_HISTORY中能够保存的会话信息的能力。ORACLE又提供AWR特性，ASH收集到的会话信息，是做为AWR中快照信息的一部分，被保存到了硬盘上。
1.2、关于AWR
AWR 是 Oracle 10g 版本 推出的新特性，全称叫Automatic Workload Repository-自动负载信息库(接替了之前的Statspack的功能，功能更加完善了)。
AWR负责收集、处理并维护性能统计信息，用于检查和分析性能问题，AWR生成的统计数据即可以通过V$视图和DBA_*数据字典查看，也可以通过脚本来生成相应报表。
2.生成分析报表
AWR 是通过对比两次快照(snapshot)收集到的统计信息，来生成报表数据，生成的报表包括多个部分，AWR在生成报告时，可以选择生成TXT或HTML两种格式的报告。可以生成的报告脚本如下：
awrrpt.sql ：生成指定快照区间的统计报表；
awrrpti.sql ：生成指定数据库实例，并且指定快照区间的统计报表；
awrsqlrpt.sql ：生成指定快照区间，指定SQL语句(实际指定的是该语句的SQLID)的统计报表；
awrsqrpi.sql ：生成指定数据库实例，指定快照区间的指定SQL语句的统计报表；
awrddrpt.sql ：指定两个不同的时间周期，生成这两个周期的统计对比报表；
awrddrpi.sql ：指定数据库实例，并指定两个的不同时间周期，生成这两个周期的统计对比报表；
注意：想要让AWR收集到准确的统计信息，从而生成可靠的性能分析报告，必须将初始化参数statistics_level的值设置为typical(默认)或all。 SQL> show parameter statistics_level; NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ statistics_level string TYPICAL SQL> |
2.1生成标准统计报表
SQL> show user; USER is "SYS" SQL> @$ORACLE_HOME/rdbms/admin/awrrpt.sql Current Instance ~~~~~~~~~~~~~~~~ DB Id DB Name Inst Num Instance ----------- ------------ -------- ------------ 1368089174 ORCL 1 orcl Specify the Report Type ~~~~~~~~~~~~~~~~~~~~~~~ Would you like an HTML report, or a plain text report? Enter 'html' for an HTML report, or 'text' for plain text Defaults to 'html' Enter value for report_type: html --此处需指定生成的报表格式，有txt和html两种选择，默认情况下为html格式 |
Type Specified: html Instances in this Workload Repository schema ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DB Id Inst Num DB Name Instance Host ------------ -------- ------------ ------------ ------------ * 1368089174 1 ORCL orcl myCentOS03 Using 1368089174 for database Id Using 1 for instance number Specify the number of days of snapshots to choose from ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Entering the number of days (n) will result in the most recent (n) days of snapshots being listed. Pressing <return> without specifying a number lists all completed snapshots. Enter value for num_days: 2 此处需指定要读取多少天内的快照信息 |
Enter value for num_days: 2 Listing the last 2 days of Completed Snapshots Snap Instance DB Name Snap Id Snap Started Level ------------ ------------ --------- ------------------ ----- orcl ORCL 204 13 Mar 2014 00:00 1 205 13 Mar 2014 01:00 1 206 13 Mar 2014 16:38 1 207 13 Mar 2014 18:00 1 208 13 Mar 2014 19:00 1 209 13 Mar 2014 20:00 1 210 13 Mar 2014 21:00 1 211 13 Mar 2014 22:00 1 212 13 Mar 2014 23:00 1 213 14 Mar 2014 00:00 1 214 14 Mar 2014 01:00 1 215 14 Mar 2014 02:00 1 216 14 Mar 2014 03:00 1 217 14 Mar 2014 04:00 1 218 14 Mar 2014 05:00 1 219 14 Mar 2014 05:42 1 220 14 Mar 2014 07:00 1 Specify the Begin and End Snapshot Ids ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Enter value for begin_snap: 217 Begin Snapshot Id specified: 217 Enter value for end_snap: 218 End Snapshot Id specified: 218 Specify the Report Name ~~~~~~~~~~~~~~~~~~~~~~~ The default report file name is awrrpt_1_217_218.html. To use this name, press <return> to continue, otherwise enter an alternative. Enter value for report_name: 此处为要生成的报告指定一个文件名，默认会根据前面输入的snap_id生成一个文件名，比如这里生成的默认文件名为awrrpt_1_217_218.html，当然DBA可以根据实际情况对文件名进行自定义。 |
可能出现的问题： declare * ERROR at line 1: ORA-20200: The instance was shutdown between snapshots 206 and 215 ORA-06512: at line 42 |
Enter value for report_name:/u01/app/oracle/awrrpt_1_217_218.html ........ End of Report </BODY></HTML> Report written to /u01/app/oracle/awrrpt_1_217_218.html |
最终生成统计报表，如下：
[oracle@myCentOS03 oracle]$ ls admin db_1 my_arch_backup oradata awrrpt_1_217_218.html flash_recovery_area my_cold_backup oraInventory [oracle@myCentOS03 oracle]$ pwd /u01/app/oracle [oracle@myCentOS03 oracle]$ 通过浏览器打开，如下所示：
|
2.2生成指定实例的数据库报表
这项统计报表一般是针对多实例数据库，前面使用的脚本是生成数据库级别的统计报表，对于多实例的数据库，有时候DBA可能希望看到某个实例的表现，那么本脚本就不能用了。
SQL> @$ORACLE_HOME/rdbms/admin/awrrpti.sql Specify the Report Type ~~~~~~~~~~~~~~~~~~~~~~~ Would you like an HTML report, or a plain text report? Enter 'html' for an HTML report, or 'text' for plain text Defaults to 'html' Enter value for report_type: |
此处需指定生成的报表格式，有txt和html两种选择，默认情况下为html格式。
Type Specified: html Instances in this Workload Repository schema ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DB Id Inst Num DB Name Instance Host ------------ -------- ------------ ------------ ------------ * 1368089174 1 ORCL orcl myCentOS03 Enter value for dbid: 1368089174 Using 1368089174 for database Id Enter value for inst_num: 1 Using 1 for instance number |
相比标准统计报表的生成，这里多了两个需指定的值，就是选择要生成报表的DBID以及实例的ID。
Specify the number of days of snapshots to choose from ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Entering the number of days (n) will result in the most recent (n) days of snapshots being listed. Pressing <return> without specifying a number lists all completed snapshots. Enter value for num_days: 2 |
指定要读取多少天内的快照信息。
Enter value for num_days: 2 Listing the last 2 days of Completed Snapshots Snap Instance DB Name Snap Id Snap Started Level ------------ ------------ --------- ------------------ ----- orcl ORCL 204 13 Mar 2014 00:00 1 205 13 Mar 2014 01:00 1 206 13 Mar 2014 16:38 1 207 13 Mar 2014 18:00 1 208 13 Mar 2014 19:00 1 209 13 Mar 2014 20:00 1 210 13 Mar 2014 21:00 1 211 13 Mar 2014 22:00 1 212 13 Mar 2014 23:00 1 213 14 Mar 2014 00:00 1 214 14 Mar 2014 01:00 1 215 14 Mar 2014 02:00 1 216 14 Mar 2014 03:00 1 217 14 Mar 2014 04:00 1 218 14 Mar 2014 05:00 1 219 14 Mar 2014 05:42 1 220 14 Mar 2014 07:00 1 Specify the Begin and End Snapshot Ids ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Enter value for begin_snap: 214 Begin Snapshot Id specified: 214 Enter value for end_snap: 215 End Snapshot Id specified: 215 Specify the Report Name ~~~~~~~~~~~~~~~~~~~~~~~ The default report file name is awrrpt_1_214_215.html. To use this name, press <return> to continue, otherwise enter an alternative. Enter value for report_name: /u01/app/oracle/awrrpt_1_214_215.html ...... End of Report </BODY></HTML> Report written to /u01/app/oracle/awrrpt_1_214_215.html |
剩下的步骤就与标准统计报表的步骤完全相同。
2.3生成指定SQL语句的统计报表
这项统计专门用来分析某条指定的SQL语句，通过awrsqrpt.sql脚本，awr能够生成指定sql(曾经执行过的SQL)的执行计划，消耗的资源等等信息，有助于DBA进行SQL调优。
具体操作如下，首先还是执行生成脚本：
SQL> @$ORACLE_HOME/rdbms/admin/awrsqrpt.sql Current Instance ~~~~~~~~~~~~~~~~ DB Id DB Name Inst Num Instance ----------- ------------ -------- ------------ 1368089174 ORCL 1 orcl Specify the Report Type ~~~~~~~~~~~~~~~~~~~~~~~ Would you like an HTML report, or a plain text report? Enter 'html' for an HTML report, or 'text' for plain text Defaults to 'html' Enter value for report_type: html Type Specified: html Instances in this Workload Repository schema ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DB Id Inst Num DB Name Instance Host ------------ -------- ------------ ------------ ------------ * 1368089174 1 ORCL orcl myCentOS03 Using 1368089174 for database Id Using 1 for instance number Specify the number of days of snapshots to choose from ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Entering the number of days (n) will result in the most recent (n) days of snapshots being listed. Pressing <return> without specifying a number lists all completed snapshots. Enter value for num_days: 2 Listing the last 2 days of Completed Snapshots Snap Instance DB Name Snap Id Snap Started Level ------------ ------------ --------- ------------------ ----- orcl ORCL 204 13 Mar 2014 00:00 1 205 13 Mar 2014 01:00 1 206 13 Mar 2014 16:38 1 207 13 Mar 2014 18:00 1 208 13 Mar 2014 19:00 1 209 13 Mar 2014 20:00 1 210 13 Mar 2014 21:00 1 211 13 Mar 2014 22:00 1 212 13 Mar 2014 23:00 1 213 14 Mar 2014 00:00 1 214 14 Mar 2014 01:00 1 215 14 Mar 2014 02:00 1 216 14 Mar 2014 03:00 1 217 14 Mar 2014 04:00 1 218 14 Mar 2014 05:00 1 219 14 Mar 2014 05:42 1 220 14 Mar 2014 07:00 1 Specify the Begin and End Snapshot Ids ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Enter value for begin_snap: 214 Begin Snapshot Id specified: 214 Enter value for end_snap: 215 End Snapshot Id specified: 215 Specify the SQL Id ~~~~~~~~~~~~~~~~~~ Enter value for sql_id: 17y8m0gj8x941 |
指定要分析的SQL_ID
批注： 首先知道当前的会话ID，如下： SQL> select sid from v$mystat where rownum=1; SID ---------- 148 SQL> select SQL_ID from v$session where sid=148; SQL_ID ------------- 17y8m0gj8x941 |
AWR自动生成分析报表
2.4生成不同时间段时的统计对比报表
在没有awr之前，如果希望对不同时间段时，数据库的整体影响进行对比，只能依靠DBA手工查询相关视图，并通过时间条件来获取差异(还有些统计已经无法对比)，而在AWR中，直接就提供了，对不同时间段时，数据库的性能统计做差异对比的功能。
执行脚本如下：
SQL> @$ORACLE_HOME/rdbms/admin/awrddrpt.sql Current Instance ~~~~~~~~~~~~~~~~ DB Id DB Id DB Name Inst Num Inst Num Instance ----------- ----------- ------------ -------- -------- ------------ 1368089174 1368089174 ORCL 1 1 orcl Specify the Report Type ~~~~~~~~~~~~~~~~~~~~~~~ Would you like an HTML report, or a plain text report? Enter 'html' for an HTML report, or 'text' for plain text Defaults to 'html' |
Enter value for report_type: html Instances in this Workload Repository schema ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DB Id Inst Num DB Name Instance Host ------------ -------- ------------ ------------ ------------ * 1368089174 1 ORCL orcl myCentOS03 Database Id and Instance Number for the First Pair of Snapshots ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Using 1368089174 for Database Id for the first pair of snapshots Using 1 for Instance Number for the first pair of snapshots |
Specify the number of days of snapshots to choose from ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Entering the number of days (n) will result in the most recent (n) days of snapshots being listed. Pressing <return> without specifying a number lists all completed snapshots. Enter value for num_days: 2 Listing the last 2 days of Completed Snapshots Snap Instance DB Name Snap Id Snap Started Level ------------ ------------ --------- ------------------ ----- orcl ORCL 204 13 Mar 2014 00:00 1 205 13 Mar 2014 01:00 1 206 13 Mar 2014 16:38 1 207 13 Mar 2014 18:00 1 208 13 Mar 2014 19:00 1 209 13 Mar 2014 20:00 1 210 13 Mar 2014 21:00 1 211 13 Mar 2014 22:00 1 212 13 Mar 2014 23:00 1 213 14 Mar 2014 00:00 1 214 14 Mar 2014 01:00 1 215 14 Mar 2014 02:00 1 216 14 Mar 2014 03:00 1 217 14 Mar 2014 04:00 1 218 14 Mar 2014 05:00 1 219 14 Mar 2014 05:42 1 220 14 Mar 2014 07:00 1 Specify the First Pair of Begin and End Snapshot Ids ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Enter value for begin_snap: 214 First Begin Snapshot Id specified: 214 Enter value for end_snap: 215 First End Snapshot Id specified: 215 |
Instances in this Workload Repository schema ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ DB Id Inst Num DB Name Instance Host ------------ -------- ------------ ------------ ------------ * 1368089174 1 ORCL orcl myCentOS03 Database Id and Instance Number for the Second Pair of Snapshots ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Using 1368089174 for Database Id for the second pair of snapshots Using 1 for Instance Number for the second pair of snapshots Specify the number of days of snapshots to choose from ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Entering the number of days (n) will result in the most recent (n) days of snapshots being listed. Pressing <return> without specifying a number lists all completed snapshots. Enter value for num_days2: 2 Listing the last 2 days of Completed Snapshots Snap Instance DB Name Snap Id Snap Started Level ------------ ------------ --------- ------------------ ----- orcl ORCL 204 13 Mar 2014 00:00 1 205 13 Mar 2014 01:00 1 206 13 Mar 2014 16:38 1 207 13 Mar 2014 18:00 1 208 13 Mar 2014 19:00 1 209 13 Mar 2014 20:00 1 210 13 Mar 2014 21:00 1 211 13 Mar 2014 22:00 1 212 13 Mar 2014 23:00 1 213 14 Mar 2014 00:00 1 214 14 Mar 2014 01:00 1 215 14 Mar 2014 02:00 1 216 14 Mar 2014 03:00 1 217 14 Mar 2014 04:00 1 218 14 Mar 2014 05:00 1 219 14 Mar 2014 05:42 1 220 14 Mar 2014 07:00 1 Specify the Second Pair of Begin and End Snapshot Ids ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Enter value for begin_snap2: 216 Second Begin Snapshot Id specified: 216 Enter value for end_snap2: 217 Second End Snapshot Id specified: 217 |
Specify the Report Name ~~~~~~~~~~~~~~~~~~~~~~~ The default report file name is awrdiff_1_214_1_216.html To use this name, press <return> to continue, otherwise enter an alternative. Enter value for report_name: /u01/app/oracle/awrdiff_1_214_1_216.html ...... Report written to /u01/app/oracle/awrdiff_1_214_1_216.html |
报表生成以后，在显示时将以并列的形式，直观的显示出两个不同时间段里，数据库各项参数的差异，摘要如图：
2.5生成指定SQL语句的统计报表
前例的对比是在单实例环境下进行的，如果希望对多实例的数据库做对比，那就要使用$ORACLE_HOME/rdbms/admin/awrddrpi.sql脚本。
3.查看AWR视图
不管是EM也好，或是前面演示中使用的awr*.sql脚本也好，实质都是访问ORACLE中的部分相关视图来生成统计数据，当然也可以直接查询动态性能视图(或相关数据字典)的方式来获取自己想要的那部分性能数据。ORACLE将这部分性能统计数据保存在DBA_HIST开头的数据字典中，要查询当前实例所有能够访问的DBA_HIST字典，可以通过下列语句：
SQL> select * from dict where table_name like ¨DBA_HIST%¨; TABLE_NAME COMMENTS ------------------------------ -------------------------------------------------------------------------------- DBA_HIST_DATABASE_INSTANCE Database Instance Information DBA_HIST_SNAPSHOT Snapshot Information DBA_HIST_SNAP_ERROR Snapshot Error Information DBA_HIST_BASELINE Baseline Metadata Information DBA_HIST_WR_CONTROL Workload Repository Control Information DBA_HIST_DATAFILE Names of Datafiles DBA_HIST_FILESTATXS Datafile Historical Statistics Information DBA_HIST_TEMPFILE Names of Temporary Datafiles DBA_HIST_TEMPSTATXS Temporary Datafile Historical Statistics Information DBA_HIST_COMP_IOSTAT I/O stats aggregated on component level DBA_HIST_SQLSTAT SQL Historical Statistics Information DBA_HIST_SQLTEXT SQL Text ...................... |