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V$EVENT_NAME
V$EVENT_NAME?displays information about wait events.
| EVENT# | NUMBER | Number of the wait event |
| EVENT_ID | NUMBER | Identifier of the wait event |
| NAME | VARCHAR2(64) | Name of the wait event |
| PARAMETER1 | VARCHAR2(64) | Description of the first parameter for the wait event |
| PARAMETER2 | VARCHAR2(64) | Description of the second parameter for the wait event |
| PARAMETER3 | VARCHAR2(64) | Description of the third parameter for the wait event |
| WAIT_CLASS_ID | NUMBER | Identifier of the class of the wait event |
| WAIT_CLASS# | NUMBER | Number of the class of the wait event |
| WAIT_CLASS | VARCHAR2(64) | Name of the class of the wait event. See?"Classes of Wait Events"?for a description of the different wait event classes. |
The WAIT_CLASS_ID, WAIT_CLASS#, and WAIT_CLASS columns are added to the?V$EVENT_NAME view in Oracle Database 10g Release 1 to group wait events by class or?category, such as User I/O, Network, Concurrency, etc. The WAIT_CLASS_ID contains the hash?value of the wait class name; it will remain the same from version to version as long as the name of?the wait class does not change. The column WAIT_CLASS# contains a unique number for the?WAIT_CLASS. Just like the EVENT#, it may change from version to version. The column?WAIT_CLASS contains the actual name of the wait event class. ?
V$SESSION_WAIT
V$SESSION_WAIT?displays the resources or events for which active sessions are waiting.
The following are tuning considerations:
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P1RAW,?P2RAW, and?P3RAW?display the same values as the?P1,?P2, and?P3?columns, except that the numbers are displayed in hexadecimal.
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The?WAIT_TIME?column contains a value of?-2?on platforms that do not support a fast timing mechanism. If you are running on one of these platforms and you want this column to reflect true wait times, then you must set the?TIMED_STATISTICS?initialization parameter totrue. Remember that doing this has a small negative effect on system performance.
In previous releases, the?WAIT_TIME?column contained an arbitrarily large value instead of a negative value to indicate the platform did not have a fast timing mechanism.
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The?STATE?column interprets the value of?WAIT_TIME?and describes the state of the current or most recent wait.
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| SID | NUMBER | Session identifier |
| SEQ# | NUMBER | Sequence number that uniquely identifies this wait. Incremented for each wait. |
| EVENT | VARCHAR2(64) | Resource or event for which the session is waiting See Also:?Appendix C, "Oracle Wait Events" |
| 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 | A nonzero value is the session's last wait time. A zero value means the session is currently waiting. |
| SECONDS_IN_WAIT | NUMBER | If?WAIT_TIME?=?0, then?SECONDS_IN_WAIT?is the seconds spent in the current wait condition. If?WAIT_TIME?>?0, then?SECONDS_IN_WAIT?is the seconds since the start of the last wait, and?SECONDS_IN_WAIT?-?WAIT_TIME?/?100?is the active seconds since the last wait ended. |
| STATE | VARCHAR2(19) | Wait state:
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The text of PARAMETER1, PARAMETER2, and PARAMETER3 of each event are also displayed?in the P1TEXT, P2TEXT, and P3TEXT columns in the V$SESSION_WAIT view whenever a?session waits on the event. The actual values for these parameters are shown in P1, P2, and P3?columns of the V$SESSION_WAIT view.
V$SYSTEM_EVENT
| EVENT | VARCHAR2(64) | Name of the wait event |
| TOTAL_WAITS | NUMBER | Total number of waits for the event |
| TOTAL_TIMEOUTS | NUMBER | Total number of timeouts for the event |
| TIME_WAITED | NUMBER | Total amount of time waited for the event (in hundredths of a second) |
| AVERAGE_WAIT | NUMBER | Average amount of time waited for the event (in hundredths of a second) |
| TIME_WAITED_MICRO | NUMBER | Total amount of time waited for the event (in microseconds) |
| EVENT_ID | NUMBER | Identifier of the wait event |
| WAIT_CLASS_ID | NUMBER | Identifier of the class of the wait event |
| WAIT_CLASS# | NUMBER | Number of the class of the wait event |
| WAIT_CLASS | VARCHAR2(64) | Name of the class of the wait event |
Note that the?TIME_WAITED?and?AVERAGE_WAIT?columns will contain a value of zero on those platforms that do not support a fast timing mechanism. If you are running on one of these platforms and you want this column to reflect true wait times, you must set?TIMED_STATISTICS?to?TRUE?in the parameter file;
The column EVENT contains the name of the wait event, and the column TOTAL_WAITS contains?the number of times the sessions waited on this event. If applicable to the event, the?TOTAL_TIMEOUTS column records the number of times a session failed to get the requested?resource after the initial wait. The column TIME_WAITED reports the total amount of time spent?waiting on the event. The column AVERAGE_WAIT gives the average time for each wait and is?derived from the TOTAL_WAITS and TIME_WAITED olumns.?
Starting with Oracle9i Database, wait time has been tracked in microseconds, that is, 1/1,000,000th?of a second, and has been reported in the TIME_WAITED_MICRO column. The TIME_WAITED?and AVERAGE_WAIT columns are derived by dividing TIME_WAITED_MICRO by 10000.?
轉載于:https://my.oschina.net/u/3862440/blog/2873054
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