1.在 Oracle 數據庫 10g 中輕鬆進行響應時間分析
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主要內容:
先，通過在 Oracle 數據庫 10g 中發出以下查詢可以大體上獲知數據庫的運行狀況：
select METRIC_NAME,
VALUE
from SYS.V_$SYSMETRIC
where METRIC_NAME IN ('Database CPU Time Ratio',
'Database Wait Time Ratio') AND
INTSIZE_CSEC =
(select max(INTSIZE_CSEC) from SYS.V_$SYSMETRIC);
METRIC_NAME VALUE
------------------------------ ----------
Database Wait Time Ratio 6
Database CPU Time Ratio 94
還可以使用以下查詢快速瞭解數據庫在前一個小時運行時整體性能是否下降過：
select end_time,
value
from sys.v_$sysmetric_history
where metric_name = 'Database CPU Time Ratio'
order by 1;
END_TIME VALUE
-------------------- ----------
22-NOV-2004 10:00:38 98
22-NOV-2004 10:01:39 96
22-NOV-2004 10:02:37 99
22-NOV-2004 10:03:38 100
22-NOV-2004 10:04:37 99
22-NOV-2004 10:05:38 77
22-NOV-2004 10:06:36 100
22-NOV-2004 10:07:37 96
22-NOV-2004 10:08:39 100
同時，您可以使用如下查詢來查詢 V$SYSMETRIC_SUMMARY 視圖以充分了解整個數據庫效率的最小值、最大值和平均值：
select CASE METRIC_NAME
WHEN 'SQL Service Response Time' then 'SQL Service Response Time (secs)'
WHEN 'Response Time Per Txn' then 'Response Time Per Txn (secs)'
ELSE METRIC_NAME
END METRIC_NAME,
CASE METRIC_NAME
WHEN 'SQL Service Response Time' then ROUND((MINVAL / 100),2)
WHEN 'Response Time Per Txn' then ROUND((MINVAL / 100),2)
ELSE MINVAL
END MININUM,
CASE METRIC_NAME
WHEN 'SQL Service Response Time' then ROUND((MAXVAL / 100),2)
WHEN 'Response Time Per Txn' then ROUND((MAXVAL / 100),2)
ELSE MAXVAL
END MAXIMUM,
CASE METRIC_NAME
WHEN 'SQL Service Response Time' then ROUND((AVERAGE / 100),2)
WHEN 'Response Time Per Txn' then ROUND((AVERAGE / 100),2)
ELSE AVERAGE
END AVERAGE
from SYS.V_$SYSMETRIC_SUMMARY
where METRIC_NAME in ('CPU Usage Per Sec',
'CPU Usage Per Txn',
'Database CPU Time Ratio',
'Database Wait Time Ratio',
'Executions Per Sec',
'Executions Per Txn',
'Response Time Per Txn',
'SQL Service Response Time',
'User Transaction Per Sec')
ORDER BY 1
METRIC_NAME MINIMUM MAXIMUM AVERAGE
------------------------------ ---------- ---------- ----------
CPU Usage Per Sec 0 7 1
CPU Usage Per Txn 1 29 8
Database CPU Time Ratio 61 100 94
Database Wait Time Ratio 0 39 5
Executions Per Sec 2 60 8
Executions Per Txn 16 164 41
Response Time Per Txn (secs) 0 .28 .08
SQL Service Response Time (sec 0 0 0
User Transaction Per Sec 0 1 0
但如果響應時間比所需的時間長，則數據庫管理員需要了解哪些用戶活動類型使數據庫運行如此困難。同樣，在 Oracle 數據庫 10g 之前，此信息更難獲得，但現在只需查詢一下即可：
select case db_stat_name when 'parse time elapsed' then 'soft parse time' else db_stat_name end db_stat_name, case db_stat_name when 'sql execute elapsed time' then time_secs - plsql_time when 'parse time elapsed' then time_secs - hard_parse_time else time_secs end time_secs, case db_stat_name when 'sql execute elapsed time' then round(100 * (time_secs - plsql_time) / db_time,2) when 'parse time elapsed' then round(100 * (time_secs - hard_parse_time) / db_time,2) else round(100 * time_secs / db_time,2) end pct_time from (select stat_name db_stat_name, round((value / 1000000),3) time_secs from sys.v_$sys_time_model where stat_name not in('DB time','background elapsed time', 'background cpu time','DB CPU')), (select round((value / 1000000),3) db_time from sys.v_$sys_time_model where stat_name = 'DB time'), (select round((value / 1000000),3) plsql_time from sys.v_$sys_time_model where stat_name = 'PL/SQL execution elapsed time'), (select round((value / 1000000),3) hard_parse_time from sys.v_$sys_time_model where stat_name = 'hard parse elapsed time') order by 2 desc; DB_STAT TIME_SECS PCT_TIME ----------------------------- --------- -------- sql execute elapsed time 13263.707 45.84 PL/SQL execution elapsed time 13234.738 45.74 hard parse elapsed time 1943.687 6.72 soft parse time 520.584 1.8 .
Oracle 現在通過等待類爲等待提供了一個摘要/彙總機制：
select WAIT_CLASS,
TOTAL_WAITS,
round(100 * (TOTAL_WAITS / SUM_WAITS),2) PCT_WAITS,
ROUND((TIME_WAITED / 100),2) TIME_WAITED_SECS,
round(100 * (TIME_WAITED / SUM_TIME),2) PCT_TIME
from
(select WAIT_CLASS,
TOTAL_WAITS,
TIME_WAITED
from V$SYSTEM_WAIT_CLASS
where WAIT_CLASS != 'Idle'),
(select sum(TOTAL_WAITS) SUM_WAITS,
sum(TIME_WAITED) SUM_TIME
from V$SYSTEM_WAIT_CLASS
where WAIT_CLASS != 'Idle')
order by 5 desc;
WAIT_CLASS TOTAL_WAITS PCT_WAITS TIME_WAITED_SECS PCT_TIME
--------------- ----------- ---------- ---------------- ----------
User I/O 2245204 7.48 4839.43 54.39
System I/O 2438387 8.12 2486.21 27.94
Application 920385 3.07 513.56 5.77
Other 39962 .13 422.36 4.75
Commit 200872 .67 284.76 3.2
Network 24133213 80.38 162.26 1.82
Concurrency 6867 .02 102.63 1.15
現在揭示批量總等待時間是由用戶 I/O 等待而導致要比嘗試和測量單個等待事件來獲得全局映像要容易得多。與響應時間度量一樣，您還可以使用如下所示的查詢按時間回顧上一小時的情況：
select to_char(a.end_time,'DD-MON-YYYY HH:MI:SS') end_time,
b.wait_class,
round((a.time_waited / 100),2) time_waited
from sys.v_$waitclassmetric_history a,
sys.v_$system_wait_class b
where a.wait_class# = b.wait_class# and
b.wait_class != 'Idle'
order by 1,2;
END_TIME WAIT_CLASS TIME_WAITED
-------------------- --------------- -----------
22-NOV-2004 11:28:37 Application 0
22-NOV-2004 11:28:37 Commit .02
22-NOV-2004 11:28:37 Concurrency 0
22-NOV-2004 11:28:37 Configuration 0
22-NOV-2004 11:28:37 Network .01
22-NOV-2004 11:28:37 Other 0
22-NOV-2004 11:28:37 System I/O .05
22-NOV-2004 11:28:37 User I/O 0
.
.
當然，您可以使用 V$SESS_TIME_MODEL 視圖只專注於一個 SID，並獲取會話的所有統計數據。還可以使用以下查詢查看使用新等待類的當前會話：
select a.sid,
b.username,
a.wait_class,
a.total_waits,
round((a.time_waited / 100),2) time_waited_secs
from sys.v_$session_wait_class a,
sys.v_$session b
where b.sid = a.sid and
b.username is not null and
a.wait_class != 'Idle'
order by 5 desc;
SID USERNAME WAIT_CLASS TOTAL_WAITS TIME_WAITED_SECS
--- ---------- --------------- ----------- ----------------
257 SYSMAN Application 356104 75.22
255 SYSMAN Commit 14508 25.76
257 SYSMAN Commit 25026 22.02
257 SYSMAN User I/O 11924 19.98
.
.
如果需要按時間回顧以發現哪些會話已被登錄並正使用最多的資源，可以使用以下查詢。在以下示例中，我們將查看從 2004 年 11 月 21 日午夜至凌晨 5 點發生的涉及用戶 I/O 等待的活動：
select sess_id, username, program, wait_event, sess_time, round(100 * (sess_time / total_time),2) pct_time_waited from (select a.session_id sess_id, decode(session_type,'background',session_type,c.username) username, a.program program, b.name wait_event, sum(a.time_waited) sess_time from sys.v_$active_session_history a, sys.v_$event_name b, sys.dba_users c where a.event# = b.event# and a.user_id = c.user_id and sample_time > '21-NOV-04 12:00:00 AM' and sample_time < '21-NOV-04 05:00:00 AM' and b.wait_class = 'User I/O' group by a.session_id, decode(session_type,'background',session_type,c.username), a.program, b.name), (select sum(a.time_waited) total_time from sys.v_$active_session_history a, sys.v_$event_name b where a.event# = b.event# and sample_time > '21-NOV-04 12:00:00 AM' and sample_time < '21-NOV-04 05:00:00 AM' and b.wait_class = 'User I/O') order by 6 desc; SESS_ID USERNAME PROGRAM WAIT_EVENT SESS_TIME PCT_TIME_WAITED ------- -------- ---------- ------------------------- ---------- ------------- 242 SYS exp@RHAT9K db file scattered read 3502978 33.49 242 SYS oracle@RHA db file sequential read 2368153 22.64 242 SYS oracle@RHA db file scattered read 1113896 10.65 243 SYS oracle@RHA db file sequential read 992168 9.49