enq: SQ - contention | 易学教程

--每分钟操作
SQL> select sql_id, mi, count(mi)
2    from (select event, sql_id, to_char(sample_time, 'yyyymmdd hh24mi') mi --,
3          --session_id
4            from dba_hist_active_sess_history
5           where sql_id = '7wxfw53bsmgpq'
6             and sample_time > to_date('20140717 0940', 'yyyymmdd hh24mi')
7             and sample_time < to_date('20140717 0950', 'yyyymmdd hh24mi'))
8   group by sql_id, mi
9    order by mi ;

SQL_ID        MI             COUNT(MI)
------------- ------------- ----------
7wxfw53bsmgpq 20140717 0942          1
7wxfw53bsmgpq 20140717 0943         23
7wxfw53bsmgpq 20140717 0944        125
7wxfw53bsmgpq 20140717 0946         96
7wxfw53bsmgpq 20140717 0947        114
7wxfw53bsmgpq 20140717 0949         44

通过图片，发现对第一条获取序列的语句比較暂用性能

--等待事件以及语句情况
SQL> select event,sql_id, mi, count(mi)
2    from (select substrb(event,1.30) event, sql_id, to_char(sample_time, 'yyyymmdd hh24mi') mi --,
3          --session_id
4            from dba_hist_active_sess_history
5           where sql_id = '7wxfw53bsmgpq'

6             and sample_time > to_date('20140717 0940', 'yyyymmdd hh24mi')
7             and sample_time < to_date('20140717 0950', 'yyyymmdd hh24mi'))
8   group by event,sql_id, mi
9    order by mi ;

EVENT                                                            SQL_ID        MI             COUNT(MI)
---------------------------------------------------------------- ------------- ------------- ----------
                                                                 7wxfw53bsmgpq 20140717 0942          1
buffer busy waits                                                7wxfw53bsmgpq 20140717 0943          1
enq: SQ - contention                                             7wxfw53bsmgpq 20140717 0943         22
buffer busy waits                                                7wxfw53bsmgpq 20140717 0944          3

enq: SQ - contention                                             7wxfw53bsmgpq 20140717 0944        122
buffer busy waits                                                7wxfw53bsmgpq 20140717 0946          2
enq: SQ - contention                                             7wxfw53bsmgpq 20140717 0946         94
buffer busy waits                                                7wxfw53bsmgpq 20140717 0947          2
enq: SQ - contention                                             7wxfw53bsmgpq 20140717 0947        112
buffer busy waits                                                7wxfw53bsmgpq 20140717 0949          1
enq: SQ - contention                                             7wxfw53bsmgpq 20140717 0949         43

--大小获取查询
SQL> select sequence_name,cache_size from dba_sequences where sequence_name like upper('%qreque%');

SEQUENCE_NAME CACHE_SIZE
------------------------------ ----------
QREQUESTNO 20 改成100 在測试

SQL>

--大小获取查询
SQL> select sequence_name,cache_size from dba_sequences where sequence_name like upper('%qreque%');

SEQUENCE_NAME CACHE_SIZE
------------------------------ ----------
QREQUESTNO 20 变100 在测试

来源：https://www.cnblogs.com/zfyouxi/p/4640703.html

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