V$SESSION_LONGOPS

对大部分DBA来说，V$SESSION_LONGOPS视图都不会陌生，以前在面试的时候，也有一些企业会问到如何查询数据库中运行时间比较长的SQL，就可以通过这个视图来查看。
V$SESSION_LONGOPS视图不但可以监控运行式时间比较长的SQL，也会记录RMAN备份、EXP/EXPDP、收集统计信息、排序等操作，基本数据库所有运行时间超过6秒的SQL都会记录在这个视图中，也有的DBA会定期检查这个视图来寻找可优化的SQL。
下面是这个视图的结构：
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SQL> desc v$session_longops
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名称 是否为空? 类型 注释
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----------------------------------------- -------- ------------------ ------------------
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SID NUMBER 和V$SESSION中的SID一样
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SERIAL# NUMBER 和V$SESSION中的SERIAL#一样
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OPNAME VARCHAR2(64) 操作的名称，如全表扫描
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TARGET VARCHAR2(64) 被操作的对象名，如表名
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TARGET_DESC VARCHAR2(32) TARGET的描述
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SOFAR NUMBER 以完成的数量，如扫描多少数据块
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TOTALWORK NUMBER 一共需要完成的数量
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UNITS VARCHAR2(32) 计量单位
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START_TIME DATE 开始时间
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LAST_UPDATE_TIME DATE 最后一次调用set_session_longops的时间
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TIMESTAMP DATE 特定操作的时间戳
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TIME_REMAINING NUMBER 预计剩余时间，单位秒
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ELAPSED_SECONDS NUMBER 开始操作到最后更新的时间
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CONTEXT NUMBER
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MESSAGE VARCHAR2(512) 对操作的描述
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USERNAME VARCHAR2(30) 操作用户的名字
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SQL_ADDRESS RAW(4) 用于关联V$SQL等视图
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SQL_HASH_VALUE NUMBER 用于关联V$SQL等视图
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SQL_ID VARCHAR2(13) 用于关联V$SQL等视图
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SQL_PLAN_HASH_VALUE NUMBER 用于关联V$SQL等视图
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SQL_EXEC_START DATE SQL开始运行的时间
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SQL_EXEC_ID NUMBER SQL执行的标识符
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SQL_PLAN_LINE_ID NUMBER SQL执行计划相关
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SQL_PLAN_OPERATION VARCHAR2(30) SQL执行计划相关
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SQL_PLAN_OPTIONS VARCHAR2(30) SQL执行计划相关
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QCSID NUMBER 并行查询
下面简单做几个超过6秒的操作，来查看下这个视图。
先测试下insert操作。
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SQL> create table longops_test as select * from dba_objects;
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表已创建。
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SQL> insert into longops_test select * from longops_test;
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已创建65525行。
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SQL> /
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已创建131050行。
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SQL> /
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已创建262100行。
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SQL> /
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已创建524200行。
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SQL> /
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已创建1048400行。
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SQL> commit;
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提交完成。
现在INSERT操作已经超过6秒，查询下V$SESSION_LONGOPS视图。
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SID SERIAL# OPNAME TARGET SOFAR TOTALWORK UNITS MESSAGE SQL_PLAN_OPERATION SQL_PLAN_OPTIONS
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--- ------- --------- ---------------- ----- -------- ----- --------------- ------------------- ---------------
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194 12 Table Scan SYS.LONGOPS_TEST 14895 14895 Blocks Table Scan: TABLE ACCESS FULL
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SYS.LONGOPS_TEST:
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14895 out of
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14895 Blocks done
这是已经运行结束的INSERT操作，可见SOFAR和TOTALWORK的值是一样的，在看下没运行完的SQL。
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SQL> create table longops_ctas as select * from longops_test;
在SQL执行6秒后(还没运行完)时，看下V$SESSION_LONGOPS视图的状态。
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SID SERIAL# OPNAME TARGET SOFAR TOTALWORK UNITS MESSAGE SQL_PLAN_OPERATION SQL_PLAN_OPTIONS
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--- ------- --------- ---------------- ----- -------- ----- --------------- ------------------- ---------------
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194 12 Table Scan SYS.LONGOPS_TEST 14895 14895 Blocks Table Scan: TABLE ACCESS FULL
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SYS.LONGOPS_TEST:
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14895 out of
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14895 Blocks done
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194 12 Table Scan SYS.LONGOPS_TEST 13275 29785 Blocks Table Scan: TABLE ACCESS FULL
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SYS.LONGOPS_TEST:
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13275 out of
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29785 Blocks done
可见，当前扫描了13275个数据块，总共需要扫描29785个数据块。RMAN备份和收集统计信息也同样会被这个视图记录。
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OPNAME SOFAR TOTALWORK MESSAGE
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--------------------------------- ---------- ---------- -------------------------------------------
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Gather Table Partition Statistics 1 1 Gather Table Partition Statistics: Table
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WR H$_OSSTAT : 1 out of 1 Partitions done
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RMAN: aggregate input 1181953 1181953 RMAN: aggregate input: backup 33: 1181953
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out of 1181953 Blocks done
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RMAN: aggregate input 1181953 1181953 RMAN: aggregate input: backup 33: 1181953
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out of 1181953 Blocks done
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RMAN: aggregate output 359461 359461 RMAN: aggregate output: backup 33: 359461
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out of 359461 Blocks done
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RMAN: full datafile backup 1181280 1181280 RMAN: full datafile backup: Set Count 18:
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1181280 out of 1181280 Blocks done
下面是ORACLE官方文档对V$SESSION_LONGOPS视图的介绍：
view source
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V$SESSION_LONGOPS displays the status of various operations that run for longer than 6 seconds (in absolute time). These operations currently include many backup and recovery functions, statistics gathering, and query execution, and more operations are added for every Oracle release.
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To monitor query execution progress, you must be using the cost-based optimizer and you must:
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?Set the TIMED_STATISTICS or SQL_TRACE parameters to true
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?Gather statistics for your objects with the DBMS_STATS package
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You can add information to this view about application-specific long-running operations by using the DBMS_APPLICATION_INFO.SET_SESSION_LONGOPS procedure.
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Column Datatype Description
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------------------- ---------- ---------------------------------------------------------------------------------
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SID NUMBER Identifier of the session processing the long-running operation. If multiple sessi
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ons are cooperating in the long-running operation, then SID corresponds to the mai
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n or master session.
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SERIAL# NUMBER Serial number of the session processing the long-running operation. If multiple se
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ssions are cooperating in the long-running operation, then SERIAL# corresponds to
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the main or master session. SERIAL# is used to uniquely identify a session's objec
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ts. Guarantees that session-level commands are applied to the correct session obje
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cts if the session ends and another session begins with the same session ID.
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OPNAME VARCHAR2(64) Brief description of the operation
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TARGET VARCHAR2(64) Object on which the operation is carried out
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TARGET_DESC VARCHAR2(32) Description of the target
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SOFAR NUMBER Units of work done so far
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TOTALWORK NUMBER Total units of work
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UNITS VARCHAR2(32) Units of measurement
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START_TIME DATE Starting time of the operation
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LAST_UPDATE_TIME DATE Time when statistics were last updated for the operation
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TIMESTAMP DATE Timestamp specific to the operation
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TIME_REMAINING NUMBER Estimate (in seconds) of time remaining for the operation to complete
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ELAPSED_SECONDS NUMBER Number of elapsed seconds from the start of the operations
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CONTEXT NUMBER Context
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MESSAGE VARCHAR2(512) Statistics summary message
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USERNAME VARCHAR2(30) User ID of the user performing the operation
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SQL_ADDRESS RAW(4 | 8) Used with the value of the SQL_HASH_VALUE column to identify the SQL statement as
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sociated with the operation
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SQL_HASH_VALUE NUMBER Used with the value of the SQL_ADDRESS column to identify the SQL statement assoc
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iated with the operation
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SQL_ID VARCHAR2(13) SQL identifier of the SQL statement associated with the long operation, if any
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SQL_PLAN_HASH_VALUE NUMBER SQL plan hash value; NULL if SQL_ID is NULL
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SQL_EXEC_START DATE Time when the execution of the SQL started; NULL if SQL_ID is NULL
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SQL_EXEC_ID NUMBER SQL execution identifier (see V$SQL_MONITOR)
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SQL_PLAN_LINE_ID NUMBER SQL plan line ID corresponding to the long operation; NULL if the long operation
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is not associated with a line of the execution plan
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SQL_PLAN_OPERATION VARCHAR2(30) Plan operation name; NULL if SQL_PLAN_LINE_ID is NULL
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SQL_PLAN_OPTIONS VARCHAR2(30) Plan operation options; NULL if SQL_PLAN_LINE_ID is NULL
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QCSID NUMBER Session identifier of the parallel coordinator