![]() These waits occur when a COMMIT is issued. In our analysis of locks and waits we are going to talk mainly about share locks, mode 4 and exclusive locks, mode 6. and high enqueue waits can indicate a sub-optimal DBWR background process. First of all, you must find out which type of enqueue is involved: - Capture VSESSIONWAIT for event 'enqueue' - Find out enqueue type select chr(bitand(P1,-16777216)/16777215) chr(bitand(P1,16711680)/65535) 'Name', bitand(P1, 65535) 'Mode' from dual Where P1 VSESSIONWAIT.P1 - Find out which SQL statement the sessions are. Exampleįinally, we can identify the SQL statements that have been waiting the most with below query. Just as Oracle sessions must inevitably wait for db file I/O, they must also wait for log file I/O. To find out the objects with the most waits we can use below SQL. enq: PE - contention) is the Parameter Enqueue, which happens after alter system or alter session statements. SUM(a.wait_time + a.time_waited) total_wait_time enq: KO - fast object checkpoint) is seem in Oracle STAR transformations and high enqueue waits can indicate a sub-optimal DBWR background process. For sessions that wait for an enqueue, REQUEST is greater than 0 and LMODE is 0.In the Oracle session overview, you can recognize the sessions that wait for an enqueue (REQUEST > 0) by the fact that they wait for an 'enqueue' wait event. ![]() To find out the users who experienced the most waits we can use below SQL. The enqueue timeouts Oracle metric is the total number of enqueue operations (get and convert) that timed out before they could complete. ![]() SUM(wait_time + time_waited) total_wait_time Oracle provides us with V$ACTIVE_SESSION_HISTORY to get information about the most common wait events, and the SQL statements, database objects, and users responsible for those waits. You want to find out the recent important waits in your database, as well as the users, SQL statements, and objects that are responsible for most of those waits.
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