Oracle Temp表空間具體使用資訊分析

1查詢臨時表空間大小

SQL>select tablespace_name,file_name,autoextensible,bytes/1024/1024,maxbytes/1024/1024 from dba_temp_files;

TABLESPACE_NAME FILE_NAME AUT BYTES/1024/1024 MAXBYTES/1024/1024

-------------------- ------------------------------------------------------------ --- --------------- ------------------

TEMP +ASMVG1/orcl/tempfile/temp.262.1005600277 YES 20 32767.9844

2.測試環境

sqlplus / as sysdba

create user myoracle identified by oracle;

grant connect,resouce to myoracle;

create table test_objs as select * from dba_objects;

exit

sqlplus myorace/oracle

select a.* ,b.* from test_objs a,test_objs b order by 1,2;

新開一會話

sqlplus / as sysdba

SQL> select username,sql_id,tablespace,segtype,extents from v$tempseg_usage;

SQL> /

USERNAME SQL_ID TABLESPACE SEGTYPE EXTENTS

------------------------------ ------------- ------------------------------- --------- ----------

MYORACLE 0a003svjmcz8t TEMP SORT 50

SQL> /

USERNAME SQL_ID TABLESPACE SEGTYPE EXTENTS

------------------------------ ------------- ------------------------------- --------- ----------

MYORACLE 0a003svjmcz8t TEMP SORT 59

使用關聯查詢可以確定正在消耗TEMP空間的sql詳細資訊

SQL> SELECT a.username, a.sid, a.serial#, a.osuser,a.schemaname,a.program,a.type,b.tablespace,b.sql_id, to_char(trunc((b.blocks * d.value) / 1024 /1024)) || ' MB' size

2 , b.segtype , c.sql_text

3 FROM v$session a, v$tempseg_usage b, v$sqlarea c

4 , (select value from v$parameter where name = 'db_block_size') d

5 WHERE a.saddr = b.session_addr

6 AND c.address= a.sql_address

7 AND c.hash_value = a.sql_hash_value

8 ORDER BY b.tablespace, b.blocks;

no rows selected

SQL> /

USERNAME SID SERIAL# OSUSER SCHEMANAME PROGRAM TYPE TABLESPACE SQL_ID SIZ SEGTYPESQL_TEXT

------------------------------ ---------- ---------- ------------------------------ ------------------------------ ------------------------------------------------ ---------- ------------------------------- ------------- ------------------------------------------- --------- ------------------------------------------------------------

MYORACLE 60 11 oracle MYORACLE sqlplus@rac1 (TNS V1-V3) USER TEMP dyk4dprp70d74 216 MB SORT select a.* ,b.* from test_objs a,test_objs b order by 1,2

SQL> /

USERNAME SID SERIAL# OSUSER SCHEMANAME PROGRAM TYPE TABLESPACE SQL_ID SIZ SEGTYPESQL_TEXT

------------------------------ ---------- ---------- ------------------------------ ------------------------------ ------------------------------------------------ ---------- ------------------------------- ------------- ------------------------------------------- --------- ------------------------------------------------------------

MYORACLE 60 11 oracle MYORACLE sqlplus@rac1 (TNS V1-V3) USER TEMP dpgnh97fq0yhu 226 MB SORT select a.* ,b.* from test_objs a,test_objs b order by 1,2

此時從檢視v$tempseg_usage;可以清楚看出臨時段的使用情況。如果該買遊戲賬號平臺地圖SQL使用了大量的temp空間必然執行很慢，可以檢視其執行計劃分析SQL語句和執行計劃作出優化處理。

select * from table(dbms_xplan.display_cursor('dyk4dprp70d74'));

select * from table(dbms_xplan.display_cursor('dpgnh97fq0yhu'));

SQL> select * from table(dbms_xplan.display_cursor('dpgnh97fq0yhu'));

PLAN_TABLE_OUTPUT

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

SQL_IDdpgnh97fq0yhu, child number 0

-------------------------------------

select a.* ,b.* from test_objs a,test_objs b order by 1,2

Plan hash value: 3670659157

-------------------------------------------------------------------------------------------

| Id| Operation | Name | Rows| Bytes |TempSpc| Cost (%CPU)| Time |

-------------------------------------------------------------------------------------------

|0 | SELECT STATEMENT | | | | | 29M(100)| |

|1 |SORT ORDER BY | |241M | 93G|102G | 29M(1) |98:51:41 |

|2 |MERGE JOIN CARTESIAN| |241M | 93G | |838K(2) | 02:47:39 |

|3 | TABLE ACCESS FULL | TEST_OBJS | 15549 |3143K| | 56(2) | 00:00:01 |

|4 | BUFFER SORT | | 15549 |3143K| | 29M(1)| 98:51:40 |

|5 | TABLE ACCESS FULL | TEST_OBJS | 15549 |3143K| | 54(2) | 00:00:01 |

-------------------------------------------------------------------------------------------

Note

-----

- dynamic sampling used for this statement (level=2)

21 rows selected.

分析執行計劃，全表掃描，笛卡爾積，笛卡爾結果集再一次做排序，都及其耗費CPU資源和I/O資源

可以進一步從ASH分析

SQL>select sql_id,SQL_PLAN_LINE_ID,SQL_PLAN_OPERATION,event,count(*) from v$active_session_history where sql_id='dpgnh97fq0yhu' group by sql_id,SQL_PLAN_LINE_ID,SQL_PLAN_OPERATION,event

SQL_ID SQL_PLAN_LINE_ID SQL_PLAN_OPERATION EVENT COUNT(*)

------------- ---------------- ------------------------------ ---------------------------------------- ----------

dpgnh97fq0yhu 4 BUFFER 2

dpgnh97fq0yhu 0 SELECT STATEMENT Disk file operations I/O 1

dpgnh97fq0yhu 0 SELECT STATEMENT control file sequential read 3

dpgnh97fq0yhu 0 SELECT STATEMENT DFS lock handle 19

dpgnh97fq0yhu 0 SELECT STATEMENT enq: CF - contention 3

dpgnh97fq0yhu 1 SORT 16

dpgnh97fq0yhu 0 SELECT STATEMENT 3

7 rows selected.

如果當前沒有SQL在使用Temp空間，則如下兩個檢視沒有資料呈現

SQL> select * from v$tempseg_usage;

no rows selected

SQL> select * from v$sort_usage;

no rows selected

一旦TEMP空間被使用，則如下兩個查詢確定TEMP空間被使用了多少

SQL> select tablespace_name,file_name,autoextensible,bytes/1024/1024,maxbytes/1024/1024 from dba_temp_files

TABLESPACE_NAME FILE_NAME AUT BYTES/1024/1024 MAXBYTES/1024/1024

------------------------------ -------------------------------------------------- --- --------------- ------------------

TEMP +ASMVG1/orcl/tempfile/temp.262.1005600277 YES 407 32767.9844

SQL> select TABLESPACE_NAME,TOTAL_BLOCKS,USED_BLOCKS,FREE_BLOCKS from v$sort_segment;

TABLESPACE_NAME TOTAL_BLOCKS USED_BLOCKS FREE_BLOCKS

------------------------------- ------------ ----------- -----------

TEMP 51456 0 51456

SQL> select 51456*8/1024 from dual;

51456*8/1024

------------

402

如果SQL正在使用TEMP空間，則查詢v$sort_segment會顯示USED_BLOCKS，此時FREE_BLOCKS

SQL>select TABLESPACE_NAME,TOTAL_BLOCKS,USED_BLOCKS,FREE_BLOCKS from v$sort_segment;

TABLESPACE_NAME TOTAL_BLOCKS USED_BLOCKS FREE_BLOCKS

------------------------------- ------------ ----------- -----------

TEMP 56960 56960

一旦佔用TEMP表空間的SQL結束，則檢視v$sort_segment資訊顯示如下所示

SQL> select TABLESPACE_NAME,TOTAL_BLOCKS,USED_BLOCKS,FREE_BLOCKS from v$sort_segment;

TABLESPACE_NAME TOTAL_BLOCKS USED_BLOCKS FREE_BLOCKS

------------------------------- ------------ ----------- -----------

TEMP 0 62336

此時TOTAL_BLOCKS和FREE_BLOCKS相同，說明此時的TEMP表空間可以繼續給其他SQL使用。

通過v$temp_space_header查詢臨時表空間已經使用過的最大空間，這個檢視是永久化的。

SQL> select TABLESPACE_NAME,sum(BYTES_USED)/1024/1024,sum(BYTES_FREE)/1024/1024from v$temp_space_header group byTABLESPACE_NAME;

TABLESPACE_NAME SUM(BYTES_USED)/1024/1024 SUM(BYTES_FREE)/1024/1024

------------------------------ ------------------------- -------------------------

TEMP 492

可以看到執行計劃的步驟1耗時最多，這也是該SQL慢的核心原因

一旦SQL語句結束，則該檢視不再有資料呈現。