每一个连接到数据库实例中的session都拥有一条记录。包括用户session及后台进程如DBWR，LGWR，arcchiver等
| Column | Datatype | Description |
| SADDR | RAW(4 | 8) | Session address |
| SID | NUMBER | Session identifier |
| SERIAL# | NUMBER | 同一个sid被重用时，serial#会增加 |
| AUDSID | NUMBER | Auditing session ID |
| PADDR | RAW(4 | 8) | 关联v$process的addr字段，可以通过这个字段查处当前session对应操作系统的进程的id |
| USER# | NUMBER | 等于dba_users中的user_id。Oracle内部进程的user#为0 |
| USERNAME | VARCHAR2(30) | 等于dba_users中的username。Oracle内部进程的username为空 |
| COMMAND | NUMBER | session正在执行的SQL ID。1代表create table，3代表select |
| OWNERID | NUMBER | The column contents are invalid if the value is 2147483644. Otherwise, this column contains the identifier of the user who owns the migratable session. |
| For operations using Parallel Slaves, interpret this value as a 4-byte value. The low-order 2 bytes of which represent the session number, and the high-order bytes the instance ID of the query coordinator. | ||
| TADDR | VARCHAR2(8) | 当前的transaction address。可以用来关联v$transaction的addr字段 |
| LOCKWAIT | VARCHAR2(8) | 可以通过这个字段查询出当前正在等待的锁的相关信息。sid & lockwait与v$lock中的sid & kaddr相对应 |
| STATUS | VARCHAR2(8) | 用来判断session状态。Active：正执行SQL语句。Inactive：等待操作。Killed：被标注为删除 |
| SERVER | VARCHAR2(9) | Server type (DEDICATED| SHARED| PSEUDO| NONE) |
| SCHEMA# | NUMBER | schema user id。Oracle内部进程的schema#为0。 |
| SCHEMANAME | VARCHAR2(30) | schema username。Oracle内部进程的schemaname为sys |
| OSUSER | VARCHAR2(30) | 客户端操作系统用户名 |
| PROCESS | VARCHAR2(12) | 客户端process id |
| MACHINE | VARCHAR2(64) | 客户端machine name |
| TERMINAL | VARCHAR2(30) | 客户端执行的terminal name |
| PROGRAM | VARCHAR2(48) | 客户端应用程序。比如ORACLE.EXE (PMON)或者sqlplus.exe |
| TYPE | VARCHAR2(10) | session type (background or user) |
| SQL_ADDRESS | RAW(4 | 8) | session正在执行的sql statement，和v$sql中的address, hash_value, sql_id, child_number相对应 |
| SQL_HASH_VALUE | NUMBER | |
| SQL_ID | VARCHAR2(13) | |
| SQL_CHILD_NUMBER | NUMBER | |
| PREV_SQL_ADDR | RAW(4 | 8) | 上一次执行的sql statement |
| PREV_HASH_VALUE | NUMBER | |
| PREV_SQL_ID | VARCHAR2(13) | |
| PREV_CHILD_NUMBER | NUMBER | |
| FIXED_TABLE_SEQUENCE | NUMBER | 当session完成一个user call后就会增加的一个数值，也就是说，如果session inactive，它就不会增加。因此可以根据此字段的值变化来监控某个时间点以来的session的性能情况。例如，一个小时以前，某个session的FIXED_TABLE_SEQUENCE是10000，而现在是20000，则表明一个小时内其user call比较频繁，可以重点关注此session的performance statistics |
| ROW_WAIT_OBJ# | NUMBER | 被锁定行所在table的object_id。和dba_objects中的object_id关联可以得到被锁定的table name |
| ROW_WAIT_FILE# | NUMBER | 被锁定行所在的datafile id。和v$datafile中的file#关联可以得到datafile name |
| ROW_WAIT_BLOCK# | NUMBER | Identifier for the block containing the row specified in ROW_WAIT_ROW#. This column is valid only if the session is currently waiting for another transaction to commit and the value of ROW_WAIT_OBJ# is not -1. |
| ROW_WAIT_ROW# | NUMBER | session当前正在等待的被锁定的行 |
| LOGON_TIME | DATE | Time of logon |
| LAST_CALL_ET | NUMBER | If the session STATUS is currently ACTIVE, then the value represents the elapsed time in seconds since the session has become active. |
| If the session STATUS is currently INACTIVE, then the value represents the elapsed time in seconds since the session has become inactive. | ||
| PDML_ENABLED | VARCHAR2(3) | This column has been replaced by column PDML_STATUS |
| FAILOVER_TYPE | VARCHAR2(13) | Indicates whether and to what extent transparent application failover (TAF) is enabled for the session: |
| NONE - Failover is disabled for this session | ||
| SESSION - Client is able to fail over its session following a disconnect | ||
| SELECT - Client is able to fail over queries in progress as well | ||
| FAILOVER_METHOD | VARCHAR2(10) | Indicates the transparent application failover method for the session: |
| NONE - Failover is disabled for this session | ||
| BASIC - Client itself reconnects following a disconnect | ||
| PRECONNECT - Backup instance can support all connections from every instance for which it is backed up | ||
| FAILED_OVER | VARCHAR2(3) | Indicates whether the session is running in failover mode and failover has occurred (YES) or not (NO) |
| RESOURCE_CONSUMER_GROUP | VARCHAR2(32) | Name of the session's current resource consumer group |
| PDML_STATUS | VARCHAR2(8) | If ENABLED, the session is in a PARALLEL DML enabled mode. If DISABLED, PARALLEL DML enabled mode is not supported for the session. If FORCED, the session has been altered to force PARALLEL DML. |
| PDDL_STATUS | VARCHAR2(8) | If ENABLED, the session is in a PARALLEL DDL enabled mode. If DISABLED, PARALLEL DDL enabled mode is not supported for the session. If FORCED, the session has been altered to force PARALLEL DDL. |
| PQ_STATUS | VARCHAR2(8) | If ENABLED, the session is in a PARALLEL QUERY enabled mode. If DISABLED, PARALLEL QUERY enabled mode is not supported for the session. If FORCED, the session has been altered to force PARALLEL QUERY. |
| CURRENT_QUEUE_DURATION | NUMBER | If queued (1), the current amount of time the session has been queued. If not currently queued, the value is 0. |
| CLIENT_IDENTIFIER | VARCHAR2(64) | Client identifier of the session |
| BLOCKING_SESSION_STATUS | VARCHAR2(11) | Blocking session status: |
| VALID | ||
| NO HOLDER | ||
| GLOBAL | ||
| NOT IN WAIT | ||
| UNKNOWN | ||
| BLOCKING_INSTANCE | NUMBER | Instance identifier of blocking session |
| BLOCKING_SESSION | NUMBER | Session identifier of blocking session |
| SEQ# | NUMBER | Sequence number that uniquely identifies the wait. Incremented for each wait. |
| EVENT# | NUMBER | Event number |
| EVENT | VARCHAR2(64) | Resource or event for which the session is waiting |
| P1TEXT | VARCHAR2(64) | Description of the first additional parameter |
| P1 | NUMBER | First additional parameter |
| P1RAW | RAW(4) | First additional parameter |
| P2TEXT | VARCHAR2(64) | Description of the second additional parameter |
| P2 | NUMBER | Second additional parameter |
| P2RAW | RAW(4) | Second additional parameter |
| P3TEXT | VARCHAR2(64) | Description of the third additional parameter |
| P3 | NUMBER | Third additional parameter |
| P3RAW | RAW(4) | Third additional parameter |
| WAIT_CLASS_ID | NUMBER | Identifier of the wait class |
| WAIT_CLASS# | NUMBER | Number of the wait class |
| WAIT_CLASS | VARCHAR2(64) | Name of the wait class |
| WAIT_TIME | NUMBER | WAIT_TIME <> 0 上次实际等待时间；WAIT_TIME=0 session正在等待当前的事件 |
| SECONDS_IN_WAIT | NUMBER | WAIT_TIME=0 SECONDS_IN_WAIT是在当前等待条件下的等待时间； WAIT_TIME>0 SECONDS_IN_WAIT是指从上次等待的起始时间到当前时间，SECONDS_IN_WAIT - WAIT_TIME /100 是从上次等待结束时间点到当前时间(即活动时间) |
| STATE | VARCHAR2(19) | Wait state:参照WAIT_TIME，SECONDS_IN_WAIT字段 |
| 0 - WAITING (session正在等待当前的事件) | ||
| -2 - WAITED UNKNOWN TIME (duration of last wait is unknown) | ||
| -1 - WAITED SHORT TIME (last wait <1/100th of a second) | ||
| >0 - WAITED KNOWN TIME (WAIT_TIME = 上次实际等待时间) | ||
| SERVICE_NAME | VARCHAR2(64) | Service name of the session |
| SQL_TRACE | VARCHAR2(8) | Indicates whether SQL tracing is enabled (ENABLED) or disabled (DISABLED) |
| SQL_TRACE_WAITS | VARCHAR2(5) | Indicates whether wait tracing is enabled (TRUE) or not (FALSE) |
| SQL_TRACE_BINDS | VARCHAR2(5) | Indicates whether bind tracing is enabled (TRUE) or not (FALSE) |
Session的信息：
SID：SESSION标识，常用于连接其它列
SERIAL#：如果某个SID又被其它的session使用的话则此数值自增加(当一个 SESSION结束，另一个SESSION开始并使用了同一个SID)。
AUDSID：审查session ID唯一性，确认它通常也用于当寻找并行查询模式
USERNAME：当前session在oracle中的用户名。 Client信息：
数据库session被一个运行在数据库服务器上或从中间服务器甚至桌面通过SQL*Net连接到数据库的客户端进程启动，下列各列提供这个客户端的信息
OSUSER：客户端操作系统用户名
MACHINE：客户端执行的机器
TERMINAL：客户端运行的终端
PROCESS：客户端进程的ID
PROGRAM：客户端执行的客户端程序
要显示用户所连接PC的 TERMINAL、OSUSER，需在该PC的ORACLE.INI或Windows中设置关键字TERMINAL，USERNAME。 Application信息：
调用DBMS_APPLICATION_INFO包以设置一些信息区分用户。这将显示下列各列。
CLIENT_INFO：DBMS_APPLICATION_INFO中设置
ACTION：DBMS_APPLICATION_INFO中设置
MODULE：DBMS_APPLICATION_INFO中设置
示例：
1.查找你的session信息
SQL> SELECT SID, OSUSER, USERNAME, MACHINE, PROCESS
2 FROM V$SESSION WHERE audsid = userenv('SESSIONID'); SID OSUSER USERNAME MACHINE PROCESS
---------- ---------- ---------- --------------- ------------
134 oracle SYS mysolaris 10100
159 Administra SYS WORKGROUP\THINK 4996:5088 2.当machine已知的情况下查找session
SQL> SELECT SID, OSUSER, USERNAME, MACHINE, TERMINAL
2 FROM V$SESSION
3 WHERE machine = 'mysolaris'; SID OSUSER USERNAME MACHINE TERMINAL
---------- ---------- ---------- --------------- ------------------------------
131 oracle mysolaris UNKNOWN
134 oracle SYS mysolaris pts/2
137 oracle mysolaris UNKNOWN
138 oracle mysolaris UNKNOWN
141 oracle mysolaris UNKNOWN
144 oracle mysolaris UNKNOWN
150 oracle mysolaris UNKNOWN
151 oracle mysolaris UNKNOWN
156 oracle mysolaris UNKNOWN
157 oracle mysolaris UNKNOWN
160 oracle mysolaris UNKNOWN SID OSUSER USERNAME MACHINE TERMINAL
---------- ---------- ---------- --------------- ------------------------------
161 oracle mysolaris UNKNOWN
162 oracle mysolaris UNKNOWN
163 oracle mysolaris UNKNOWN
164 oracle mysolaris UNKNOWN
165 oracle mysolaris UNKNOWN
166 oracle mysolaris UNKNOWN
167 oracle mysolaris UNKNOWN
168 oracle mysolaris UNKNOWN
169 oracle mysolaris UNKNOWN
170 oracle mysolaris UNKNOWN 21 rows selected. SQL>
V$SESSION是基础视图，常常同其他视图协同工作，如：v$lock，v$sqlarea，v$sqltext等