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1、oracle中查找执行效率低下的SQLv$sqltext：存储的是完整的SQL,SQL被分割v$sqlarea：存储的SQL 和一些相关的信息，比如累计的执行次数，逻辑读，物理读等统计信息（统计）v$sql：内存共享SQL区域中已经解析的SQL语句。（即时）根据sid查找完整sql语句：select sql_text from v$sqltext a where a.hash_value = (select sql_hash_value from v$session b where b.sid = &sid )order by piece ascselect a.CPU_TIME,-CPU时间
2、 百万分之一（微秒） a.OPTIMIZER_MODE,-优化方式 a.EXECUTIONS,-执行次数 a.DISK_READS,-读盘次数 a.SHARABLE_MEM,-占用shared pool的内存多少 a.BUFFER_GETS,-读取缓冲区的次数 a.COMMAND_TYPE,-命令类型(3:select,2:insert;6:update;7delete;47:pl/sql程序单元) a.SQL_TEXT,-Sql语句 a.SHARABLE_MEM, a.PERSISTENT_MEM, a.RUNTIME_MEM, a.PARSE_CALLS, a.DISK_READS, a.
3、DIRECT_WRITES, a.CONCURRENCY_WAIT_TIME, a.USER_IO_WAIT_TIME from SYS.V_$SQLAREA aWHERE PARSING_SCHEMA_NAME = CHEA_FILL-表空间order by a.CPU_TIME desc引用：http:/ b.username username,a.disk_reads reads,a.executions exec,a.disk_reads/decode(a.executions,0,1,a.executions) rds_exec_ratio,a.sql_text Statementf
4、rom v$sqlarea a,dba_users bwhere a.parsing_user_id=b.user_idand a.disk_reads 100000order by a.disk_reads desc;用buffer_gets列来替换disk_reads列可以得到占用最多内存的sql语句的相关信息。v$sql：内存共享SQL区域中已经解析的SQL语句。（即时）列出使用频率最高的5个查询：select sql_text,executionsfrom (select sql_text,executions,rank() over(order by executions desc)
5、 exec_rankfrom v$sql)where exec_rank =5;消耗磁盘读取最多的sql top5：select disk_reads,sql_textfrom (select sql_text,disk_reads,dense_rank() over(order by disk_reads desc) disk_reads_rankfrom v$sql)where disk_reads_rank =5;找出需要大量缓冲读取（逻辑读）操作的查询：select buffer_gets,sql_textfrom (select sql_text,buffer_gets,dense_
6、rank() over(order by buffer_gets desc) buffer_gets_rankfrom v$sql)where buffer_gets_rank=5;v$sqlarea字段定义：http:/ thousand characters of the SQL text for the current cursorSQL_IDVARCHAR2(13)SQL identifier of the parent cursor in the library cacheSHARABLE_MEMNUMBERAmount of shared memory used by a curs
7、or. If multiple child cursors exist, then the sum of all shared memory used by all child cursors.PERSISTENT_MEMNUMBERFixed amount of memory used for the lifetime of an open cursor. If multiple child cursors exist, the fixed sum of memory used for the lifetime of all the child cursors.RUNTIME_MEMNUMB
8、ERFixed amount of memory required during execution of a cursor. If multiple child cursors exist, the fixed sum of all memory required during execution of all the child cursors.SORTSNUMBERSum of the number of sorts that were done for all the child cursorsVERSION_COUNTNUMBERNumber of child cursors tha
9、t are present in the cache under this parentLOADED_VERSIONSNUMBERNumber of child cursors that are present in the cache and have their context heap (KGL heap 6) loadedOPEN_VERSIONSNUMBERThe number of child cursors that are currently open under this current parentUSERS_OPENINGNUMBERNumber of users tha
10、t have any of the child cursors openFETCHESNUMBERNumber of fetches associated with the SQL statementEXECUTIONSNUMBERTotal number of executions, totalled over all the child cursorsEND_OF_FETCH_COUNTNUMBERNumber of times this cursor was fully executed since the cursor was brought into the library cach
11、e. The value of this statistic is not incremented when the cursor is partially executed, either because it failed during the execution or because only the first few rows produced by this cursor are fetched before the cursor is closed or re-executed. By definition, the value of the END_OF_FETCH_COUNT
12、 column should be less or equal to the value of the EXECUTIONS column.USERS_EXECUTINGNUMBERTotal number of users executing the statement over all child cursorsLOADSNUMBERNumber of times the object was loaded or reloadedFIRST_LOAD_TIMEVARCHAR2(19)Timestamp of the parent creation timeINVALIDATIONSNUMB
13、ERTotal number of invalidations over all the child cursorsPARSE_CALLSNUMBERSum of all parse calls to all the child cursors under this parentDISK_READSNUMBERSum of the number of disk reads over all child cursorsDIRECT_WRITESNUMBERSum of the number of direct writes over all child cursorsBUFFER_GETSNUM
14、BERSum of buffer gets over all child cursorsAPPLICATION_WAIT_TIMENUMBERApplication wait timeCONCURRENCY_WAIT_TIMENUMBERConcurrency wait timeCLUSTER_WAIT_TIMENUMBERCluster wait timeUSER_IO_WAIT_TIMENUMBERUser I/O Wait TimePLSQL_EXEC_TIMENUMBERPL/SQL execution timeJAVA_EXEC_TIMENUMBERJava execution timeROWS_PROCESSEDNUMBERTotal number of rows processed on behalf of this SQL statementCOMMAND_TYPENUMBEROracle command type definitionOPTIMIZER_MODEVARCHAR2(25)Mode under which the SQL statement was executed
