查看scn headroom变化趋势的几种方法

查看scn headroom变化趋势的几种方法

scn headroom问题，本文不做解释。

本文为自己的总结，脚本来自于oracle sr技术工程师。

转载请注明出处http://blog.csdn.net/msdnchina/article/details/38404501

第一个方法：查询smon_scn_time表获得。

conn / as sysdba 
set numwidth 17 
set pages 1000 
alter session set nls_date_format='DD/Mon/YYYY HH24:MI:SS'; 
with t1 as( 
select time_dp , 24*60*60*(time_dp - lag(time_dp) over (order by time_dp)) timediff, 
scn - lag(scn) over(order by time_dp) scndiff 
from smon_scn_time 
) 
select time_dp , timediff, scndiff, 
trunc(scndiff/timediff) rate_per_sec 
from t1 
order by 1; 

第二个方法：查询awr报告的信息：


1. 通过How to extract the historical values of a statistic from AWR Repository (Doc ID 948272.1) 
将Script 部分复制到您生成数据库两个实例本地，命名为 例如 awr.sql 


该脚本为：

set trimspool on
set pages 50000
set lines 132
set tab off
set feedback off


clear break compute;
repfooter off;
ttitle off;
btitle off;
set timing off veri off space 1 flush on pause off termout on numwidth 10;
set echo off feedback off pagesize 50000 linesize 1000 newpage 1 recsep off;
set trimspool on trimout on;


-- 
-- Request the DB Id and Instance Number, if they are not specified


column instt_num  heading "Inst Num"  format 99999;
column instt_name heading "Instance"  format a12;
column dbb_name   heading "DB Name"   format a12;
column dbbid      heading "DB Id"     format a12 just c;
column host       heading "Host"      format a20;


prompt
prompt
prompt instances IN this workload repository SCHEMA
prompt ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SELECT DISTINCT ( CASE
                    WHEN cd.dbid = wr.dbid
                         AND cd.name = wr.db_name
                         AND ci.instance_number = wr.instance_number
                         AND ci.instance_name = wr.instance_name THEN '* '
                    ELSE '  '
                  END )
                || wr.dbid         dbbid,
                wr.instance_number instt_num,
                wr.db_name         dbb_name,
                wr.instance_name   inst_name,
                wr.host_name       host
FROM   dba_hist_database_instance wr,
       v$database cd,
       v$instance ci;


prompt
prompt USING &&dbid FOR DATABASE id
-- 
--  Set up the binds for dbid and instance_number
variable dbid NUMBER;
BEGIN
    :dbid := &dbid;
END;
/
--  Error reporting
whenever SQLERROR EXIT;
variable max_snap_time CHAR(10);
DECLARE
    CURSOR cidnum IS
      SELECT 'X'
      FROM   dba_hist_database_instance
      WHERE  dbid = :dbid;
    CURSOR csnapid IS
      SELECT To_char(Max(end_interval_time), 'dd/mm/yyyy')
      FROM   dba_hist_snapshot
      WHERE  dbid = :dbid;
    vx CHAR(1);
BEGIN
    -- Check Database Id/Instance Number is a valid pair
    OPEN cidnum;


    FETCH cidnum INTO vx;


    IF cidnum%NOTFOUND THEN
      Raise_application_error(-20200, 'Database/Instance '
                                      || :dbid
                                      || '/'
                                      ||
      ' does not exist in DBA_HIST_DATABASE_INSTANCE');
    END IF;


    CLOSE cidnum;


    -- Check Snapshots exist for Database Id/Instance Number
    OPEN csnapid;


    FETCH csnapid INTO :max_snap_time;


    IF csnapid%NOTFOUND THEN
      Raise_application_error(-20200,
      'No snapshots exist for Database/Instance '
      ||:dbid
      ||'/');
    END IF;


    CLOSE csnapid;
END;
/


whenever SQLERROR CONTINUE;
-- 
--  Ask how many days of snapshots to display
set termout ON;
column instart_fmt noprint;
column inst_name format a12 heading 'Instance';
column db_name format a12 heading 'DB Name';
column snap_id format 99999990 heading 'Snap Id';
column snapdat format a18 heading 'Snap Started' just c;
column lvl format 99 heading 'Snap|Level';
prompt
prompt
prompt specify the NUMBER OF days OF snapshots TO choose FROM
prompt ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
prompt entering the NUMBER OF days (n) will result IN the most recent
prompt (n) days OF snapshots being listed. pressing  without
prompt specifying a NUMBER LISTS ALL completed snapshots.
prompt
prompt
set heading OFF;
column num_days new_value num_days noprint;
SELECT 'Listing '
       || Decode(Nvl('&&num_days', 3.14), 0, 'no snapshots',
                                          3.14, 'all Completed Snapshots',
                                          1,
          'the last day''s Completed Snapshots',
          'the last &num_days days of Completed Snapshots'
          ),
       Nvl('&&num_days', 3.14) num_days
FROM   sys.dual;


set heading ON;
-- 
-- List available snapshots
break ON inst_name ON db_name ON host ON instart_fmt skip 1;
ttitle OFF;
SELECT To_char(s.startup_time, 'dd Mon "at" HH24:mi:ss')   instart_fmt,
       di.instance_name                                    inst_name,
       di.db_name                                          db_name,
       s.snap_id                                           snap_id,
       To_char(s.end_interval_time, 'dd Mon YYYY HH24:mi') snapdat,
       s.snap_level                                        lvl
FROM   dba_hist_snapshot s,
       dba_hist_database_instance di
WHERE  s.dbid = :dbid
       AND di.dbid = :dbid
       AND di.dbid = s.dbid
       AND di.instance_number = s.instance_number
       AND di.startup_time = s.startup_time
       AND s.end_interval_time >= Decode(&num_days, 0, To_date('31-JAN-9999',
                                                       'DD-MON-YYYY'
                                                       ),
                                                    3.14, s.end_interval_time,
                                                    To_date(:max_snap_time,
                                                    'dd/mm/yyyy')
                                                    - ( &num_days - 1 ))
ORDER  BY db_name,
          instance_name,
          snap_id;


clear break;
ttitle OFF;
-- 
--  Ask for the snapshots Id's which are to be compared
prompt
prompt
prompt specify the BEGIN AND END SNAPSHOT ids
prompt ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
prompt BEGIN SNAPSHOT id specified: &&begin_snap
prompt
prompt END SNAPSHOT id specified: &&end_snap
prompt
-- 
--  Set up the snapshot-related binds
-- 
variable bid NUMBER;
variable eid NUMBER;
BEGIN
    :bid := &begin_snap;


    :eid := &end_snap;
END;
/


prompt
-- 
--  Ask for Statistics Name Filter
-- 
prompt
prompt
prompt search statistic
prompt ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
prompt search BY STATISTICS name. pressing  without
prompt specifying anything show ALL STATISTICS.
set heading OFF;
column stat_search new_value stat_search noprint;
SELECT 'Statistic Name Filter: '
       || Nvl('&&stat_search', '%'),
       Nvl('&&stat_search', '%') stat_search
FROM   sys.dual;


set heading ON;
column stat_id heading "Statistic ID" format 9999999999999;
column name heading "Statistic Name" format a64;
column class_name heading "Statistic Class" format a10;
SELECT stat_id,
       ( CASE
           WHEN class = 1 THEN 'USER'
           WHEN class = 2 THEN 'REDO'
           WHEN class = 4 THEN 'ENQUEUE'
           WHEN class = 8 THEN 'CACHE'
           WHEN class = 16 THEN 'OS'
           WHEN class = 32 THEN 'RAC'
           WHEN class = 40 THEN 'RAC-CACHE'
           WHEN class = 64 THEN 'SQL'
           WHEN class = 72 THEN 'SQL-CACHE'
           WHEN class = 128 THEN 'DEBUG'
           ELSE To_char(class)
         END ) CLASS_NAME,
       name
FROM   v$sysstat
WHERE  Upper(name) LIKE Trim(Upper('%&stat_search%'))
ORDER  BY class,
          name
/


-- 
--  Ask for the statistics
variable stat_filter_id NUMBER
variable stat_filter_name VARCHAR2(64)
prompt
prompt
prompt specify the STATISTICS
prompt ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
prompt enter STATISTICS id OR STATISTICS name.
prompt
BEGIN
    SELECT To_number('&&stat_input')
    INTO   :stat_filter_id
    FROM   dual;
EXCEPTION
    WHEN invalid_number THEN
      :stat_filter_name := '&stat_input';
END;
/


prompt STATISTICS specified : &&stat_input
column end_interval_time heading 'Snap Started' format a18 just c;
column dbid heading 'DB Id' format a12 just c;
column instance_number heading 'Inst|Num' format 99999;
column elapsed heading 'Elapsed' format 999999;
column stat_value heading 'Stat Value' format 999999999999
column stat_name heading 'Stat Name' format a64 just l;
SELECT snap_id,
       To_char(dbid)                                     DBID,
       instance_number,
       elapsed,
       To_char(end_interval_time, 'dd Mon YYYY HH24:mi') END_INTERVAL_TIME,
       --stat_name,
       ( CASE
           WHEN stat_value > 0 THEN stat_value
           ELSE 0
         END )                                           STAT_VALUE
FROM   (SELECT snap_id,
               dbid,
               instance_number,
               elapsed,
               end_interval_time,
               stat_name,
               ( stat_value - Lag (stat_value, 1, stat_value)
                                over (
                                  PARTITION BY dbid, instance_number
                                  ORDER BY snap_id) ) AS STAT_VALUE
        FROM   (SELECT snap_id,
                       dbid,
                       instance_number,
                       elapsed,
                       end_interval_time,
                       stat_name,
                       SUM(stat_value) AS STAT_VALUE
                FROM   (SELECT X.snap_id,
                               X.dbid,
                               X.instance_number,
                               Trunc(SN.end_interval_time, 'mi')
                               END_INTERVAL_TIME,
                               X.stat_name,
                               Trunc(( Cast(SN.end_interval_time AS DATE) -
                                       Cast(SN.begin_interval_time AS DATE) ) *
                                     86400)                      ELAPSED,
                               ( CASE
                                   WHEN ( X.stat_name = :stat_filter_name
                                           OR X.stat_id = :stat_filter_id ) THEN
                                   X.value
                                   ELSE 0
                                 END )                           AS STAT_VALUE
                        FROM   dba_hist_sysstat X,
                               dba_hist_snapshot SN,
                               (SELECT instance_number,
                                       Min(startup_time) STARTUP_TIME
                                FROM   dba_hist_snapshot
                                WHERE  snap_id BETWEEN :bid AND :eid
                                GROUP  BY instance_number) MS
                        WHERE  X.snap_id = sn.snap_id
                               AND X.dbid = sn.dbid
                               AND x.dbid = :dbid
                               AND x.snap_id BETWEEN :bid AND :eid
                               AND SN.startup_time = MS.startup_time
                               AND SN.instance_number = MS.instance_number
                               AND X.instance_number = sn.instance_number
                               AND ( X.stat_name = :stat_filter_name
                                      OR X.stat_id = :stat_filter_id ))
                GROUP  BY snap_id,
                          dbid,
                          instance_number,
                          elapsed,
                          end_interval_time,
                          stat_name));




undefine dbid
undefine num_days
undefine begin_snap
undefine end_snap
undefine stat_id
undefine stat_search
undefine stat_filter_name
undefine stat_filter_id
undefine stat_input 


---该脚本结束。

2. 在SQLPLUS中运行该脚本，并根据您系统实际情况输入 




instances IN this workload repository SCHEMA 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 


DB Id Inst Num DB Name INST_NAME Host 
------------ -------- ------------ ---------------- -------------------- 
* 1163866261 1 RBIG5 RBIG5 xxx 
m 


Enter value for dbid: 1163866261 《=====输入实例ID 
USING 1163866261 FOR DATABASE 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 without 
specifying a NUMBER LISTS ALL completed snapshots. 




Enter value for num_days: 2 <===输入AWR采样天数 




specify the BEGIN AND END SNAPSHOT ids 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
Enter value for begin_snap: 1605 
BEGIN SNAPSHOT id specified: 1605 《===根据对话输入起始snapshot 序号 


Enter value for end_snap: 1639 
END SNAPSHOT id specified: 1639《===根据对话输入结束snapshot 序号 








search statistic 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
search BY STATISTICS name. pressing without 
specifying anything show ALL STATISTICS. 
Enter value for stat_search: calls to kcmgas 《======输入需要显示的统计项： calls to kcmgas 


Statistic Name Filter: calls to kcmgas 


Statistic ID Statistic Statistic Name 
-------------- ---------- ---------------------------------------------------------------- 
4072914524 DEBUG calls to kcmgas 




specify the STATISTICS 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
enter STATISTICS id OR STATISTICS name. 


Enter value for stat_input: 4072914524 《======输入统计项返回的ID 






最后，将返回一个列表，例如 


Inst 
Snap Id DB Id Num Elapsed Snap Started Stat Value 
--------- ------------ ------ ------- ------------------ ------------- 
1605 1163866261 1 3600 08 Sep 2013 00:00 0 
1606 1163866261 1 3601 08 Sep 2013 01:00 170 
1607 1163866261 1 3600 08 Sep 2013 02:00 164 
。。。 
1626 1163866261 1 3600 08 Sep 2013 21:00 155 
1627 1163866261 1 3600 08 Sep 2013 22:00 165 
1628 1163866261 1 3600 08 Sep 2013 23:00 2065《===如果有类似跳变发生,则表示数据库内部交易产生的剧烈变化，非DBLINK造成。 
。。。 
1636 1163866261 1 3600 09 Sep 2013 07:00 145 
1637 1163866261 1 3601 09 Sep 2013 08:00 174 
1638 1163866261 1 3600 09 Sep 2013 09:00 156 
1639 1163866261 1 3600 09 Sep 2013 10:00 142 

请提供您的输出结果来作为SCN 非外部数据库DBLINK造成跳变的调查结果。 



第三个方法：查询v$archived_log视图（前提是数据库开启归档模式）

set numwidth 17 
set pages 1000 
alter session set nls_date_format='DD/Mon/YYYY HH24:MI:SS'; 
SELECT tim, gscn, 
round(rate), 
round((chk16kscn - gscn)/24/3600/16/1024,1) "Headroom" 
FROM 
( 
select tim, gscn, rate, 
(( 
((to_number(to_char(tim,'YYYY'))-1988)*12*31*24*60*60) + 
((to_number(to_char(tim,'MM'))-1)*31*24*60*60) + 
(((to_number(to_char(tim,'DD'))-1))*24*60*60) + 
(to_number(to_char(tim,'HH24'))*60*60) + 
(to_number(to_char(tim,'MI'))*60) + 
(to_number(to_char(tim,'SS'))) 
) * (16*1024)) chk16kscn 
from 
( 
select FIRST_TIME tim , FIRST_CHANGE# gscn, 
((NEXT_CHANGE#-FIRST_CHANGE#)/ 
((NEXT_TIME-FIRST_TIME)*24*60*60)) rate 
from v$archived_log 
where (next_time > first_time) 
) 
) 
order by 1,2 
;