本篇文章給大家分享的是有關(guān)如何理解DBMS_RESULT_CACHE管理結(jié)果緩存的包，小編覺得挺實(shí)用的，因此分享給大家學(xué)習(xí)，希望大家閱讀完這篇文章后可以有所收獲，話不多說，跟著小編一起來看看吧。
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Oracle 11g提供了DBMS_RESULT_CACHE包來查詢SQL結(jié)果緩存內(nèi)容的狀態(tài)和適當(dāng)?shù)乜刂芐QL結(jié)果緩存內(nèi)容。
DBMS_RESULT_CACHE功能和存儲過程
功能/存儲過程 描述
STATUS： 返回結(jié)果緩存的當(dāng)前狀態(tài)。值包括：
ENABLED： 結(jié)果緩存是激活的。
DISABLED：結(jié)果緩存是不可用的。
BYPASSED：結(jié)果緩存暫時不可用。
SYNC： 結(jié)果緩存是可用的，但是目前正與其他RAC節(jié)點(diǎn)重新同步。
MEMORY_REPORT： 列出結(jié)果緩存內(nèi)存利用的一個概要（默認(rèn)）或詳細(xì)的報表。
FLUSH： 推出整個結(jié)果緩存的內(nèi)容。
INVALIDATE： 使結(jié)果緩存中一個特定對象的緩存結(jié)果無效。
INVALIDATE_OBJECT： 根據(jù)緩存ID使一特定結(jié)果緩存無效。
下面通過具體的實(shí)驗給予介紹：
一 STATUS： 返回結(jié)果緩存的當(dāng)前狀態(tài)。
yang@rac1>select dbms_result_cache.status() from dual;
DBMS_RESULT_CACHE.STATUS()
--------------------------------------------------------
ENABLED
二 MEMORY_REPORT： 列出結(jié)果緩存內(nèi)存利用的一個概要（默認(rèn)）或詳細(xì)的報表。視圖v$result_cache_statistics 是MEMORY_REPORT相同的描述
yang@rac1>exec dbms_result_cache.memory_report();
R e s u l t C a c h e M e m o r y R e p o r t
[Parameters]
Block Size = 1K bytes
Maximum Cache Size = 15744K bytes (15744 blocks)
Maximum Result Size = 787K bytes (787 blocks)
[Memory]
Total Memory = 12704 bytes [0.001% of the Shared Pool]
... Fixed Memory = 12704 bytes [0.001% of the Shared Pool]
... Dynamic Memory = 0 bytes [0.000% of the Shared Pool]
PL/SQL procedure successfully completed.
yang@rac1>select * from v$result_cache_statistics;
ID NAME VALUE
---------- ------------------------------ ---------------------------------------------------------------------------------
1 Block Size (Bytes) 1024
2 Block Count Maximum 15744
3 Block Count Current 0
4 Result Size Maximum (Blocks) 787
5 Create Count Success 0
6 Create Count Failure 0
7 Find Count 0
8 Invalidation Count 0
9 Delete Count Invalid 0
10 Delete Count Valid 0
11 Hash Chain Length 0
12 Global Hit Count 0
13 Global Miss Count 0
13 rows selected.
yang@rac1>set autotrace on
yang@rac1>select /*+ result_cache */ count(*) from yangobj;
COUNT(*)
----------
74484
Execution Plan
----------------------------------------------------------
Plan hash value: 362321706
------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Cost (%CPU)| Time |
------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 297 (1)| 00:00:04 |
| 1 | RESULT CACHE | 7uz1ww4x7gs2a6ba4qjauzt4bq | | | |
| 2 | SORT AGGREGATE | | 1 | | |
| 3 | TABLE ACCESS FULL| YANGOBJ | 61204 | 297 (1)| 00:00:04 |
------------------------------------------------------------------------------------------
Result Cache Information (identified by operation id):
------------------------------------------------------
1 - column-count=1; dependencies=(YANG.YANGOBJ); attributes=(single-row); name="select /*+ result_cache */ count(*) from yangobj"
Note
-----
- dynamic sampling used for this statement (level=2)
Statistics
----------------------------------------------------------
9 recursive calls
4 db block gets
1126 consistent gets
0 physical reads
548 redo size
528 bytes sent via SQL*Net to client
520 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
yang@rac1>/
COUNT(*)
----------
74484
Execution Plan
----------------------------------------------------------
Plan hash value: 362321706
------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Cost (%CPU)| Time |
------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 297 (1)| 00:00:04 |
| 1 | RESULT CACHE | 7uz1ww4x7gs2a6ba4qjauzt4bq | | | |
| 2 | SORT AGGREGATE | | 1 | | |
| 3 | TABLE ACCESS FULL| YANGOBJ | 61204 | 297 (1)| 00:00:04 |
------------------------------------------------------------------------------------------
Result Cache Information (identified by operation id):
------------------------------------------------------
1 - column-count=1; dependencies=(YANG.YANGOBJ); attributes=(single-row); name="select /*+ result_cache */ count(*) from yangobj"
Note
-----
- dynamic sampling used for this statement (level=2)
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
0 consistent gets
0 physical reads
0 redo size
528 bytes sent via SQL*Net to client
520 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
從視圖v$result_cache_objects中獲取CACHE_ID。
yang@rac1>select name,status,cache_id from v$result_cache_objects;
NAME STATUS CACHE_ID
------------------------------ --------- -----------------------------------
YANG.YANGOBJ Published YANG.YANGOBJ
select /*+ result_cache */ cou Published7uz1ww4x7gs2a6ba4qjauzt4bq
nt(*) from yangobj
三 INVALIDATE_OBJECT： 根據(jù)緩存ID--CACHE_ID使一特定結(jié)果緩存無效。
yang@rac1>exec DBMS_RESULT_CACHE.INVALIDATE_OBJECT('7uz1ww4x7gs2a6ba4qjauzt4bq');
PL/SQL procedure successfully completed.
yang@rac1>select name,status,cache_id from v$result_cache_objects;
NAME STATUS CACHE_ID
------------------------------ --------- -----------------------------------
YANG.YANGOBJ Published YANG.YANGOBJ
select /*+ result_cache */ cou Invalid 7uz1ww4x7gs2a6ba4qjauzt4bq
nt(*) from yangobj
四 FLUSH： 清理整個結(jié)果緩存的內(nèi)容。
yang@rac1>exec dbms_result_cache.memory_report();
R e s u l t C a c h e M e m o r y R e p o r t
[Parameters]
Block Size = 1K bytes
Maximum Cache Size = 2080K bytes (2080 blocks)
Maximum Result Size = 104K bytes (104 blocks)
[Memory]
Total Memory = 107812 bytes [0.049% of the Shared Pool]
... Fixed Memory = 9460 bytes [0.004% of the Shared Pool]
... Dynamic Memory = 98352 bytes [0.045% of the Shared Pool]
....... verhead = 65584 bytes
....... Cache Memory = 32K bytes (32 blocks)
........... Unused Memory = 26 blocks
........... Used Memory = 6 blocks
............... Dependencies = 3 blocks (3 count)
............... Results = 3 blocks
................... SQL = 2 blocks (2 count)
................... Invalid = 1 blocks (1 count)
PL/SQL 過程已成功完成。
已用時間: 00: 00: 00.35
yang@rac1>exec dbms_result_cache.flush();
PL/SQL 過程已成功完成。
已用時間: 00: 00: 00.02
yang@rac1>exec dbms_result_cache.memory_report();
R e s u l t C a c h e M e m o r y R e p o r t
[Parameters]
Block Size = 1K bytes
Maximum Cache Size = 2080K bytes (2080 blocks)
Maximum Result Size = 104K bytes (104 blocks)
[Memory]
Total Memory = 9460 bytes [0.004% of the Shared Pool]
... Fixed Memory = 9460 bytes [0.004% of the Shared Pool]
... Dynamic Memory = 0 bytes [0.000% of the Shared Pool]
PL/SQL 過程已成功完成。
已用時間: 00: 00: 00.02
結(jié)果緩存已被清除。
以上就是如何理解DBMS_RESULT_CACHE管理結(jié)果緩存的包，小編相信有部分知識點(diǎn)可能是我們?nèi)粘９ぷ鲿姷交蛴玫降?。希望你能通過這篇文章學(xué)到更多知識。更多詳情敬請關(guān)注創(chuàng)新互聯(lián)行業(yè)資訊頻道。
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