Tuesday, 25 December 2012

some event and wait events of session


SQL> select count(*),event from v$active_session_history where session_id=331 group by event order by count(*) desc;

  COUNT(*) EVENT
---------- ----------------------------------------------------------------
       323 log file sync
       220 db file sequential read
       132 log file switch (checkpoint incomplete)
       110 buffer busy waits

2.            Today, Log File related wait events are not there. Below are the wait events:

SQL> select EVENT,TOTAL_WAITS,TIME_WAITED from v$session_event where sid=331 order by time_waited desc;
                
EVENT                                                            TOTAL_WAITS TIME_WAITED
---------------------------------------------------------------- ----------- -----------
SQL*Net message from dblink                                            32615     1785828
local write wait                                                        2048      199947
enq: RO - fast object reuse                                              154       45023
events in waitclass Other                                                229       22289
db file sequential read                                                33768       17814
db file scattered read                                                  4436        9435


wait events in detail:

a.            SQL*Net message from dblink: This happens when data is fetched using DB links. This
               happenes over Network due to architecture.
b.            local write wait: This arise when consecutive Truncate statements are written.
c.             enq: RO - fast object reuse: this is because of Truncate statements.

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