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User I/O: Waits for reading blocks from disk Two key wait classes are the Application and User I/O wait classes. Oracle Wait Events That Everyone Should Know The Commit class contains just the log file sync wait information. This type of situation usually occurs when the data on the table is accessed by using index, not full table scan, as a result of single block reading. Although theres a large number of wait events, some the most common wait events are the following: Buffer busy waits: These occur when multiple processes attempt to concurrently access the same buffers in the buffer cache. Information about wait events is displayed in three dynamic performance views: V$SESSION_WAIT displays the events for which sessions have just completed waiting or are currently waiting. https://ittutorial.org/how-to-analyze-an-awr-report-in-oracle-4-top-sql/. SELECT * FROM (SELECT sql_fulltext, sql_id, elapsed_time, child_number, disk_reads, executions, first_load_time, last_load_time FROM v$sql ORDER BY elapsed_time DESC) WHERE ROWNUM < 10 /. Db file scattered read: These are waits incurred by an user process for a physical I/O to return when reading buffers into the SGA buffer cache. select a.sid,substr (b.username,1,10) username,substr (b.osuser,1,10) osuser, substr (b.program||b.module,1,15) program,substr (b.machine,1,22) machine, Top 5 wait events from v$active_session_history select * from ( select WAIT_CLASS , EVENT, count (sample_time) as EST_SECS_IN_WAIT from For such requirements, we have the below query to find out Top 5 wait events in the database. Required fields are marked *. top 5 If this value is high, it means that the Oracle instance spends most of the time on the CPU. The reads are single block reads and are usually because of indexed reads. How to identify recent WAIT events in In order to solve this problem, the memory should be increased, parallel operations should not be done unless required, and pay attention to Lob segments reads. Webquery to find top 5 wait events in oracle Author: Published on: schulferien mecklenburg vorpommern 2022 June 1, 2022 Published in: lungenarzt berlin neuklln gropius passagen 5544 views Less than a minute 1. Example SELECT a.user_id, u.username, s.sql_text, SUM(a.wait_time + a.time_waited) total_wait_time FROM v$active_session_history a, v$sqlarea s, dba_users u WHERE a.sql_id = s.sql_id AND a.user_id = u.user_id GROUP BY a.user_id, s.sql_text,