v$session,v$process,v$mystat,v$statname剖析（还算不错）
v$session,v$process,v$mystat,v$statname剖析
2012-09-27 14:39:52
分类： Oracle
SQL> select spid from v$session s, v$process p, v$mystat m
where s.paddr=p.addr and s.sid=m.sid and m.statistic#=0;
SPID
------------
26156
或者：
SQL> select spid from v$session s inner join v$process p on s.paddr=p.addr
inner join v$mystat m on s.sid=m.sid and m.statistic#=0;
SPID
------------
26156
或者：
SQL> select spid from v$process where addr in (select paddr from v$session where
sid=(select sid from v$mystat where rownum=1));
SPID
------------
26156
1)V$PROCESS
This view contains information about the currently active processes. While the LATCHWAIT column indicates what latch a process is waiting for, the LATCHSPIN column indicates what latch a process is spinning on. On multi-processor machines, Oracle processes will spin on a latch before waiting on it.
| Column | Datatype | Description |
|---|---|---|
| ADDR | RAW(4 | 8) | Address of process state object |
| PID | NUMBER | Oracle process identifier |
| SPID | VARCHAR2(12) | Operating system process identifier |
| USERNAME | VARCHAR2(15) | Operating system process username. Any two-task user coming across the network has "-T" appended to the username. |
| SERIAL# | NUMBER | Process serial number |
| TERMINAL | VARCHAR2(30) | Operating system terminal identifier |
| PROGRAM | VARCHAR2(48) | Program in progress |
| TRACEID | VARCHAR2(255) | Trace file identifier |
| BACKGROUND | VARCHAR2(1) | 1 for a background process; NULL for a normal process |
| LATCHWAIT | VARCHAR2(8) | Address of latch the process is waiting for; NULL if none |
| LATCHSPIN | VARCHAR2(8) | Address of the latch the process is spinning on; NULL if none |
| PGA_USED_MEM | NUMBER | PGA memory currently used by the process |
| PGA_ALLOC_MEM | NUMBER | PGA memory currently allocated by the process (including free PGA memory not yet released to the operating system by the server process) |
| PGA_FREEABLE_MEM | NUMBER | Allocated PGA memory which can be freed |
| PGA_MAX_MEM | NUMBER | Maximum PGA memory ever allocated by the process |
2)V$MYSTAT
This view contains statistics on the current session.
| Column | Datatype | Description |
|---|---|---|
| SID | NUMBER | ID of the current session |
| STATISTIC# | NUMBER | Number of the statistic |
| VALUE | NUMBER | Value of the statistic |
3)V$STATNAME
This view displays decoded statistic names for the statistics shown in the V$SESSTAT and V$SYSSTAT tables.
On some platforms, the NAME and CLASS columns contain additional operating system-specific statistics.
| Column | Datatype | Description |
|---|---|---|
| STATISTIC# | NUMBER | Statistic number Note: Statistics numbers are not guaranteed to remain constant from one release to another. Therefore, you should rely on the statistics name rather than its number in your applications. |
| NAME | VARCHAR2(64) | Statistic name |
| CLASS | NUMBER | A number representing one or more statistics classes. The following class numbers are additive:
|
| STAT_ID | NUMBER | Identifier of the statistic |
SQL> column name for a35;
SQL> select * from v$statname where rownum<20;
STATISTIC# NAME CLASS STAT_ID
---------- ----------------------------------- ---------- ----------
0 logons cumulative 1 2666645286
1 logons current 1 3080465522
2 opened cursors cumulative 1 85052502
3 opened cursors current 1 2301954928
4 user commits 1 582481098
5 user rollbacks 1 3671147913
6 user calls 1 2882015696
7 recursive calls 1 2656001462
8 recursive cpu usage 1 4009879262
9 session logical reads 1 3143187968
10 session stored procedure space 1 895486831
11 CPU used when call started 128 572264820
12 CPU used by this session 1 24469293
13 DB time 1 3649082374
14 cluster wait time 1 2432034337
15 concurrency wait time 1 3868577743
16 application wait time 1 1099569955
17 user I/O wait time 1 3332107451
18 session connect time 1 1678473874
19 rows selected.
从上面的查询可以看出STATISTIC# =0 的含义是自实例启动以来用户登录数据库次数的累计值。其实在查询
select spid from v$session s inner join v$process p on s.paddr=p.addr
inner join v$mystat m on s.sid=m.sid and m.statistic#=0; 中m.statistic#=1,2,3都可以，
只不过是为了得到唯一的 m.sid 而言。
另外：
通过连接查询v$mystat和v$statname就可以得到当前session的各种信息：
SQL> select m.*,n.name,n.class from v$mystat m inner join v$statname n on
m.statistic#=n.statistic# where rownum<20;
SID STATISTIC# VALUE NAME CLASS
---------- ---------- ---------- ----------------------------------- ----------
147 0 1 logons cumulative 1
147 1 1 logons current 1
147 2 353 opened cursors cumulative 1
147 3 10 opened cursors current 1
147 4 0 user commits 1
147 5 0 user rollbacks 1
147 6 389 user calls 1
147 7 7155 recursive calls 1
147 8 152 recursive cpu usage 1
147 9 3818 session logical reads 1
147 10 0 session stored procedure space 1
147 11 196 CPU used when call started 128
147 12 197 CPU used by this session 1
147 13 463 DB time 1
147 14 0 cluster wait time 1
147 15 0 concurrency wait time 1
147 16 0 application wait time 1
147 17 71 user I/O wait time 1
147 18 0 session connect time 1
19 rows selected.
4)V$SESSION
SQL> select count(column_name) from dba_tab_columns where table_name='V_$SESSION';
COUNT(COLUMN_NAME)
------------------
76
我们看到v$session视图有76列，十分的复杂。我们稍微看一下比较重要的列。
This view lists session information for each current session.
| Column | Datatype | Description |
|---|---|---|
| SADDR | RAW(4 | 8) | Session address |
| SID | NUMBER | Session identifier |
| PADDR | RAW(4 | 8) | Address of the process that owns the session |
| USER# | NUMBER | Oracle user identifier |
| USERNAME | VARCHAR2(30) | Oracle username |
| TADDR | VARCHAR2(8) | Address of transaction state object |
| LOCKWAIT | VARCHAR2(8) | Address of lock waiting for; null if none ...... |
| STATUS | VARCHAR2(8) | Status of the session:
|
| SERVER | VARCHAR2(9) | Server type (DEDICATED| SHARED| PSEUDO| NONE) |
| SCHEMA# | NUMBER | Schema user identifier |
| SCHEMANAME | VARCHAR2(30) | Schema user name |
| OSUSER | VARCHAR2(30) | Operating system client user name |
| PROCESS | VARCHAR2(12) | Operating system client process ID |
| MACHINE | VARCHAR2(64) | Operating system machine name |
| TERMINAL | VARCHAR2(30) | Operating system terminal name |
| PROGRAM | VARCHAR2(48) | Operating system program name |
| TYPE | VARCHAR2(10) | Session type |
| SQL_ADDRESS | RAW(4 | 8) | Used with SQL_HASH_VALUE to identify the SQL statement that is currently being executed |
| SQL_HASH_VALUE | NUMBER | Used with SQL_ADDRESS to identify the SQL statement that is currently being executed |
| SQL_ID | VARCHAR2(13) | SQL identifier of the SQL statement that is currently being executed |
| SQL_CHILD_NUMBER | NUMBER | Child number of the SQL statement that is currently being executed ...... |
| 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 | A nonzero value is the session's last wait time. A zero value means the session is currently waiting. |
| SECONDS_IN_WAIT | NUMBER | |
| STATE | VARCHAR2(19) | Wait state:
|
| 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) |