ASH（Active Session History）——概述（1）！

1、大家都知道v$session裡面記錄的是活動會話當前的等待，這個也可以透過v$session_wait檢視，而v$session_wait_history記錄的也只是活動會話的最近10次等待事件。

2、那麼想要看活動Session更早的等待事件就只能透過ASH了，ASH的資訊透過檢視v$active_session_history檢視。

3、使用ASH報告可以以幾分鐘為跨度對進行精確分析。ASH資訊是儲存在SGA記憶體中的。

4、我們還可以對一個會話ID、一個SQL_ID、一個程式做他們各自的ASH報告。（ashrpti.sql）

@?/rdbms/admin/ashrpt.sql

    [oracle@linux oracle]$ sqlplus / as sysdba @?/rdbms/admin/ashrpt.sql

    SQL*Plus: Release 10.2.0.4.0 - Production on 星期二 11月 1 06:36:43 2011

    Copyright (c) 1982, 2007, Oracle. All Rights Reserved.


    連線到:
    Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - Production
    With the Partitioning, OLAP, Data Mining and Real Application Testing options


    Current Instance
    ~~~~~~~~~~~~~~~~

       DB Id    DB Name      Inst Num Instance
    ----------- ------------ -------- ------------
     1293815896 ORCL                1 orcl


    Specify the Report Type
    ~~~~~~~~~~~~~~~~~~~~~~~
    Enter 'html' for an HTML report, or 'text' for plain text
    Defaults to 'html'
    輸入 report_type 的值: html   --生成html格式的ash報告。

    Type Specified: html


    Instances in this Workload Repository schema
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

       DB Id     Inst Num DB Name      Instance     Host
    ------------ -------- ------------ ------------ ------------
    * 1293815896        1 ORCL         orcl         linux

    Defaults to current database

    Using database id: 1293815896

    Defaults to current instance

    Using instance number: 1


    ASH Samples in this Workload Repository schema
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    Oldest ASH sample available: 01-11月-11 03:34:14 [    183 mins in the past]
    Latest ASH sample available: 01-11月-11 06:36:43 [      0 mins in the past]


    Specify the timeframe to generate the ASH report
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Enter begin time for report:

    --    Valid input formats:
    --      To specify absolute begin time:
    --        [MM/DD[/YY]] HH24:MI[:SS]
    --        Examples: 02/23/03 14:30:15
    --                  02/23 14:30:15
    --                  14:30:15
    --                  14:30
    --      To specify relative begin time: (start with '-' sign)
    --        -[HH24:]MI
    --        Examples: -1:15 (SYSDATE - 1 Hr 15 Mins)
    --                  -25    (SYSDATE - 25 Mins)

    Defaults to -15 mins
    輸入 begin_time 的值: -30       --採集30分鐘以前的資料。
    Report begin time specified: -30

    Enter duration in minutes starting from begin time:
    Defaults to SYSDATE - begin_time
    Press Enter to analyze till current time
    輸入 duration 的值:           --這裡預設是當前時間。
    Report duration specified:

    Using 01-11月-11 06:07:51 as report begin time
    Using 01-11月-11 06:38:17 as report end time


    Specify Slot Width (using ashrpti.sql) for 'Activity Over Time' section
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    -- Explanation:
    --   In the 'Activity Over Time' section of the ASH report,
    --   the analysis period is divided into smaller slots
    --   and top wait events are reported in each of those slots.

    -- Default:
    --   The analysis period will be automatically split upto 10 slots
    --   complying to a minimum slot width of
    --     1 minute, if the source is V$ACTIVE_SESSION_HISTORY or
    --     5 minutes, if the source is DBA_HIST_ACTIVE_SESS_HISTORY.


    Specify Slot Width in seconds to use in the 'Activity Over Time' section:
    Defaults to a value as explained above:
    Slot Width specified:


    Specify Report Targets (using ashrpti.sql) to generate the ASH report
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    -- Explanation:
    --   ASH Report can accept "Report Targets",
    --   like a particular SQL statement, or a particular SESSION,
    --   to generate the report on. If one or more report targets are
    --   specified, then the data used to generate the report will only be
    --   the ASH samples that pertain to ALL the specified report targets.

    -- Default:
    --   If none of the report targets are specified,
    --   then the target defaults to all activity in the database instance.


    Specify SESSION_ID (eg: from V$SESSION.SID) report target:
    Defaults to NULL:
    SESSION report target specified:


    Specify SQL_ID (eg: from V$SQL.SQL_ID) report target:
    Defaults to NULL: (% and _ wildcards allowed)
    SQL report target specified:


    Specify WATI_CLASS name (eg: from V$EVENT_NAME.WAIT_CLASS) report target:
    [Enter 'CPU' to investigate CPU usage]
    Defaults to NULL: (% and _ wildcards allowed)
    WAIT_CLASS report target specified:


    Specify SERVICE_HASH (eg: from V$ACTIVE_SERVICES.NAME_HASH) report target:
    Defaults to NULL:
    SERVICE report target specified:


    Specify MODULE name (eg: from V$SESSION.MODULE) report target:
    Defaults to NULL: (% and _ wildcards allowed)
    MODULE report target specified:


    Specify ACTION name (eg: from V$SESSION.ACTION) report target:
    Defaults to NULL: (% and _ wildcards allowed)
    ACTION report target specified:


    Specify CLIENT_ID (eg: from V$SESSION.CLIENT_IDENTIFIER) report target:
    Defaults to NULL: (% and _ wildcards allowed)
    CLIENT_ID report target specified:


    Specify PLSQL_ENTRY name (eg: "SYS.DBMS_LOB.*") report target:
    Defaults to NULL: (% and _ wildcards allowed)
    PLSQL_ENTRY report target specified:

    Specify the Report Name
    ~~~~~~~~~~~~~~~~~~~~~~~
    The default report file name is ashrpt_1_1101_0638.html. To use this name,
    press <return> to continue, otherwise enter an alternative.
    輸入 report_name 的值: /u01/app/oracle/ash.html           --生成報告的路徑。
    ... ...
    ... ...
    ... ...
    Report written to /u01/app/oracle/ash.html

ASH（Active Session History）——概述（1）！

ASH（Active Session History）——概述（1）！

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