Oracle常見問題集(三)

151. 如何監控 SGA 中字典緩衝區的命中率?

select parameter, gets,Getmisses , getmisses/(gets+getmisses)*100

"miss ratio",

(1-(sum(getmisses)/ (sum(gets)+sum(getmisses))))*100 "Hit ratio"

from v$rowcache

where gets+getmisses <>0

group by parameter, gets, getmisses;

152. 如何監控 SGA 中共用緩存區的命中率,應該小於 1% ?

select sum(pins) "Total Pins", sum(reloads) "Total Reloads",

sum(reloads)/sum(pins) *100 libcache

from v$librarycache;

select sum(pinhits-reloads)/sum(pins) "hit

radio",sum(reloads)/sum(pins) "reload percent"

from v$librarycache;

153. 如何顯示所有資料庫物件的類別和大小?

select count(name) num_instances ,type ,sum(source_size)

source_size ,

sum(parsed_size) parsed_size ,sum(code_size) code_size

,sum(error_size) error_size,

sum(source_size) +sum(parsed_size) +sum(code_size)

+sum(error_size) size_required

from dba_object_size

group by type order by 2;

154. 監控 SGA 中重做日誌緩存區的命中率,應該小於 1%

SELECT name, gets, misses, immediate_gets, immediate_misses,

Decode(gets,0,0,misses/gets*100) ratio1,

Decode(immediate_gets+immediate_misses,0,0,

immediate_misses/(immediate_gets+immediate_misses)*100) ratio2

FROM v$latch WHERE name IN ('redo allocation', 'redo copy');

155. 監控記憶體和硬碟的排序比率,最好使它小於 .10 ,增加 sort_area_size

SELECT name, value FROM v$sysstat WHERE name IN ('sorts (memory)',

'sorts (disk)');

156. 如何監控當前資料庫誰在運行什麽 SQL 語句?

SELECT osuser, username, sql_text from v$session a, v$sqltext b

where a.sql_address =b.address order by address, piece;

157. 如何監控字典緩衝區?

SELECT (SUM(PINS - RELOADS)) / SUM(PINS) "LIB CACHE" FROM

V$LIBRARYCACHE;

SELECT (SUM(GETS - GETMISSES - USAGE - FIXED)) / SUM(GETS) "ROW

CACHE" FROM V$ROWCACHE;

SELECT SUM(PINS) "EXECUTIONS", SUM(RELOADS) "CACHE MISSES WHILE

EXECUTING" FROM V$LIBRARYCACHE;

後者除以前者 , 此比率小於 1%, 接近 0% 爲好。

SELECT SUM(GETS) "DICTIONARY GETS",SUM(GETMISSES) "DICTIONARY

CACHE GET MISSES"

FROM V$ROWCACHE

158. 監控 MTS

select busy/(busy+idle) "shared servers busy" from v$dispatcher;

此值大於 0.5 時,參數需加大

select sum(wait)/sum(totalq) "dispatcher waits" from v$queue where

type='dispatcher';

select count(*) from v$dispatcher;

select servers_highwater from v$mts;

servers_highwater 接近 mts_max_servers 時,參數需加大

159. 如何知道當前用戶的 ID 號

SQL>SHOW USER;

OR

SQL>select user from dual;

160. 如何查看碎片程度高的表

SELECT segment_name table_name , COUNT(*) extents

FROM dba_segments WHERE owner NOT IN ('SYS', 'SYSTEM') GROUP BY

segment_name

HAVING COUNT() = (SELECT MAX( COUNT() ) FROM dba_segments GROUP

BY segment_name);

162. 如何知道表在表空間中的存儲情況

select segment_name,sum(bytes),count(*) ext_quan from dba_extents

where

tablespace_name='&tablespace_name' and segment_type='TABLE' group

by tablespace_name,segment_name;

163. 如何知道索引在表空間中的存儲情況

select segment_name,count(*) from dba_extents where

segment_type='INDEX' and owner='&owner'

group by segment_name;

164 、如何知道使用 CPU 多的用戶 session

11 是 cpu used by this session

select a.sid,spid,status,substr(a.program,1,40)

prog,a.terminal,osuser,value/60/100 value

from v$session a,v$process b,v$sesstat c

where c.statistic#=11 and c.sid=a.sid and a.paddr=b.addr order by

value desc;

165. 如何知道監聽器日誌文件

以 8I 爲例

$ORACLE_HOME/NETWORK/LOG/LISTENER.LOG

166. 如何知道監聽器參數文件

以 8I 爲例

$ORACLE_HOME/NETWORK/ADMIN/LISTENER.ORA

167. 如何知道 TNS 連接文件

以 8I 爲例

$ORACLE_HOME/NETWORK/ADMIN/TNSNAMES.ORA

168. 如何知道 Sql*Net 環境文件

以 8I 爲例

$ORACLE_HOME/NETWORK/ADMIN/SQLNET.ORA

169. 如何知道警告日誌文件

以 8I 爲例

$ORACLE_HOME/ADMIN/SID/BDUMP/SIDALRT.LOG

170. 如何知道基本結構

以 8I 爲例

$ORACLE_HOME/RDBMS/ADMIN/STANDARD.SQL

171. 如何知道建立資料字典視圖

以 8I 爲例

$ORACLE_HOME/RDBMS/ADMIN/CATALOG.SQL

172. 如何知道建立審計用資料字典視圖

以 8I 爲例

$ORACLE_HOME/RDBMS/ADMIN/CATAUDIT.SQL

173. 如何知道建立快照用資料字典視圖

以 8I 爲例

$ORACLE_HOME/RDBMS/ADMIN/CATSNAP.SQL

本講主要講的是 SQL 語句的優化方法 ! 主要基於 ORACLE9I 的 .

174. /+ALL_ROWS/

表明對語句塊選擇基於開銷的優化方法 , 並獲得最佳吞吐量 , 使資源消耗最小化 .

例如 :

SELECT /+ALL+_ROWS/ EMP_NO,EMP_NAM,DAT_IN FROM BSEMPMS WHERE

EMP_NO='CCBZZP';

<P c

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