Oracle中V$SESSION等各表的字段解释，Oracle官方解释

一、常用的视图

1.会话相关视图

View	Description
V$PROCESS	Contains information about the currently active processes
V$SESSION	Lists session information for each current session
V$SESS_IO	Contains I/O statistics for each user session
V$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. More operations are added for every Oracle Database release.
V$SESSION_WAIT	Displays the current or last wait for each session
V$SESSION_WAIT_HISTORY	Lists the last ten wait events for each active session
V$WAIT_CHAINS	Displays information about blocked sessions
V$SESSTAT	Contains session statistics
V$RESOURCE_LIMIT	Provides information about current and maximum global resource utilization for some system resources
V$SQLAREA	Contains statistics about shared SQL areas. Contains one row for each SQL string. Provides statistics about SQL statements that are in memory, parsed, and ready for execution

2.锁相关的视图：

View	Description
V$LOCK	Lists the locks currently held by Oracle Database and outstanding requests for a lock or latch
DBA_BLOCKERS	Displays a session if it is holding a lock on an object for which another session is waiting
DBA_WAITERS	Displays a session if it is waiting for a locked object
DBA_DDL_LOCKS	Lists all DDL locks held in the database and all outstanding requests for a DDL lock
DBA_DML_LOCKS	Lists all DML locks held in the database and all outstanding requests for a DML lock
DBA_LOCK	Lists all locks or latches held in the database and all outstanding requests for a lock or latch
DBA_LOCK_INTERNAL	Displays a row for each lock or latch that is being held, and one row for each outstanding request for a lock or latch
V$LOCKED_OBJECT	Lists all locks acquired by every transaction on the system
V$SESSION_WAIT	Lists the resources or events for which active sessions are waiting
V$SYSSTAT	Contains session statistics
V$RESOURCE_LIMIT	Provides information about current and maximum global resource utilization for some system resources
V$SQLAREA	Contains statistics about shared SQL area and contains one row for each SQL string. Also provides statistics about SQL statements that are in memory, parsed, and ready for execution
V$LATCH	Contains statistics for nonparent latches and summary statistics for parent latches

二、V$SESSION

https://docs.oracle.com/en/database/oracle/oracle-database/12.2/refrn/V-SESSION.html#GUID-28E2DC75-E157-4C0A-94AB-117C205789B9

三、V$SESSION_WAIT

https://docs.oracle.com/en/database/oracle/oracle-database/12.2/refrn/V-SESSION_WAIT.html#GUID-4EDAB293-F3FC-40FE-BC75-4FEE6A4D7705

这里面有个event字段，event字段的枚举值可以存在下面的表中，可以这样查询：

SELECT name, wait_class FROM V$EVENT_NAME ORDER BY name

1. 查询会话正在等待行锁的会话：

select event,sid,p1,p2,p3 from v$session_wait where event='enq: TX - row lock contention';

三、V$LOCKED_OBJECT

1.简介及表字段

该表列出每个事务获取到的所有锁。它可以展示出哪个会话正在持有锁，在什么对象上持有锁，以及锁的模式。

Column	Datatype	Description
XIDUSN	NUMBER	Undo segment number
XIDSLOT	NUMBER	Slot number
XIDSQN	NUMBER	Sequence number
OBJECT_ID	NUMBER	Object ID being locked
SESSION_ID	NUMBER	Session ID
ORACLE_USERNAME	VARCHAR2(128)	Oracle user name
OS_USER_NAME	VARCHAR2(128)	Operating system user name
PROCESS	VARCHAR2(24)	Operating system process ID
LOCKED_MODE	NUMBER	Lock mode. The numeric values for this column map to these text values for the lock modes for table locks: 0 - NONE: lock requested but not yet obtained 1 - NULL 2 - ROWS_S (SS): Row Share Lock 3 - ROW_X (SX): Row Exclusive Table Lock 4 - SHARE (S): Share Table Lock 5 - S/ROW-X (SSX): Share Row Exclusive Table Lock 6 - Exclusive (X): Exclusive Table Lock See Also: Oracle Database Concepts for more information about lock modes for table locks
CON_ID	NUMBER	The ID of the container to which the data pertains. Possible values include: 0: This value is used for rows containing data that pertain to the entire CDB. This value is also used for rows in non-CDBs. 1: This value is used for rows containing data that pertain to only the root n: Where n is the applicable container ID for the rows containing data

2.查询持有锁的会话

SELECT USERNAME, LOCKWAIT, STATUS, MACHINE, PROGRAM
 
  FROM V$SESSION
 
 WHERE SID IN (SELECT SESSION_ID FROM V$LOCKED_OBJECT);

3.查询持有锁的会话正在执行的sql

SELECT
    SQL_TEXT
FROM
    V$SQL
WHERE
    HASH_VALUE IN (
        SELECT
            SQL_HASH_VALUE
        FROM
            V$SESSION
        WHERE
            SID IN (
                SELECT
                    SESSION_ID
                FROM
                    V$LOCKED_OBJECT
            )
    );

4.根据对象名查询持有该锁对象的会话

SELECT o.object_name,s.sid, s.serial#
       FROM v$locked_object l, dba_objects o, v$session s
            WHERE l.object_id　= o.object_id
                  AND l.session_id = s.sid
 
      AND o.object_name='SEATINFORMATION';

SEATINFORMATION为本地表的名字。
 

5.根据对象名查询持有该锁对象的会话及sql

 

SELECT o.object_name,s.sid, s.serial#,s.SQL_HASH_VALUE,v.*
       FROM v$locked_object l, dba_objects o, v$session s, V$SQL v
            WHERE l.object_id　= o.object_id
                  AND l.session_id = s.sid and s.SQL_HASH_VALUE = v.HASH_VALUE
 
      AND o.object_name='INCIDENTINFORMATION';

四、V$LOCK

1.简介

该视图列出当前被oracle持有的锁。

Column	Datatype	Description
ADDR	RAW(4 | 8)	Address of lock state object
KADDR	RAW(4 | 8)	Address of lock
SID	NUMBER	Identifier for session holding or acquiring the lock
TYPE	VARCHAR2(2)	Type of user or system lock The locks on the user types are obtained by user applications. Any process that is blocking others is likely to be holding one of these locks. The user type locks are: TM - DML enqueue TX - Transaction enqueue UL - User supplied The system type locks are listed in Table 8-1. Be aware that not all types of locks are documented. To find a complete list of locks for the current release, query the V$LOCK_TYPE data dictionary view, described on "V$LOCK_TYPE". -- 我们主要关注TX 和TM 两种类型的锁 --UL 锁用户自己定义的，一般很少会定义，基本不用关注
ID1	NUMBER	Lock identifier #1 (depends on type)
ID2	NUMBER	Lock identifier #2 (depends on type) --- 当lock type 为TM 时，id1 为DML-locked object 的object_id --- 当lock type 为TX 时，id1 为usn+slot ，而id2 为seq 。 -- 当lock type 为其它时，不用关注
LMODE	NUMBER	Lock mode in which the session holds the lock: 0 - none 1 - null (NULL) 2 - row-S (SS) 3 - row-X (SX) 4 - share (S) 5 - S/Row-X (SSX) 6 - exclusive (X)--大于0时表示 当前会话以某种模式 占有 该锁，等于0时表示当前会话正在等待该锁资源，即表示该会话被阻塞。 --大于0时表示 当前会话以某种模式 占有 该锁，等于0时表示当前会话正在等待该锁资源，即表示该会话被阻塞。 往往在发生TX 锁时，伴随着TM 锁，比如一个sid=9 会话拥有一个TM 锁，一般会拥有一个或几个TX锁，但他们的id1 和id2 是不同的，请注意
REQUEST	NUMBER	Lock mode in which the process requests the lock: 0 - none 1 - null (NULL) 2 - row-S (SS) 3 - row-X (SX) 4 - share (S) 5 - S/Row-X (SSX) 6 - exclusive (X) -- 大于0时，表示当前会话被阻塞，其它会话占有该锁的模式
CTIME	NUMBER	Time since current mode was granted
BLOCK	NUMBER	Indicates whether the lock in question is blocking other processes. The possible values are: 0 - The lock is not blocking any other processes 1 - The lock is blocking other processes 2 - The lock is not blocking any blocked processes on the local node, but it may or may not be blocking processes on remote nodes. This value is used only in Oracle Real Application Clusters (Oracle RAC) configurations (not in single instance configurations).
CON_ID	NUMBER	The ID of the container to which the data pertains. Possible values include: 0: This value is used for rows containing data that pertain to the entire CDB. This value is also used for rows in non-CDBs. 1: This value is used for rows containing data that pertain to only the root n: Where n is the applicable container ID for the rows containing data

2.一个本地的死锁案例：

从oracle服务器的trace日志中看到：

会话432和会话188互相等待。

以下是相关信息：

2.1 会话432的持有的锁，被锁的对象，正在执行的sql：

SELECT *  FROM V$LOCK l where  l.sid = ;

https://logicalread.com/diagnosing-oracle-wait-for-tx-enqueue-mode-6-mc01/#.XBUGJM7_zIU