Monthly Archives: Ноябрь 2012

Useful scripts: Log file switch frequency statistsic

Very nice and easy to use query.

SELECT trunc(first_time) "Date",
 to_char(first_time, 'Dy') "Day",
 count(1) "Total",
 SUM(decode(to_char(first_time, 'hh24'), '00', 1, 0)) "h0",
 SUM(decode(to_char(first_time, 'hh24'), '01', 1, 0)) "h1",
 SUM(decode(to_char(first_time, 'hh24'), '02', 1, 0)) "h2",
 SUM(decode(to_char(first_time, 'hh24'), '03', 1, 0)) "h3",
 SUM(decode(to_char(first_time, 'hh24'), '04', 1, 0)) "h4",
 SUM(decode(to_char(first_time, 'hh24'), '05', 1, 0)) "h5",
 SUM(decode(to_char(first_time, 'hh24'), '06', 1, 0)) "h6",
 SUM(decode(to_char(first_time, 'hh24'), '07', 1, 0)) "h7",
 SUM(decode(to_char(first_time, 'hh24'), '08', 1, 0)) "h8",
 SUM(decode(to_char(first_time, 'hh24'), '09', 1, 0)) "h9",
 SUM(decode(to_char(first_time, 'hh24'), '10', 1, 0)) "h10",
 SUM(decode(to_char(first_time, 'hh24'), '11', 1, 0)) "h11",
 SUM(decode(to_char(first_time, 'hh24'), '12', 1, 0)) "h12",
 SUM(decode(to_char(first_time, 'hh24'), '13', 1, 0)) "h13",
 SUM(decode(to_char(first_time, 'hh24'), '14', 1, 0)) "h14",
 SUM(decode(to_char(first_time, 'hh24'), '15', 1, 0)) "h15",
 SUM(decode(to_char(first_time, 'hh24'), '16', 1, 0)) "h16",
 SUM(decode(to_char(first_time, 'hh24'), '17', 1, 0)) "h17",
 SUM(decode(to_char(first_time, 'hh24'), '18', 1, 0)) "h18",
 SUM(decode(to_char(first_time, 'hh24'), '19', 1, 0)) "h19",
 SUM(decode(to_char(first_time, 'hh24'), '20', 1, 0)) "h20",
 SUM(decode(to_char(first_time, 'hh24'), '21', 1, 0)) "h21",
 SUM(decode(to_char(first_time, 'hh24'), '22', 1, 0)) "h22",
 SUM(decode(to_char(first_time, 'hh24'), '23', 1, 0)) "h23",
 round(count(1) / 24, 2) "Avg"
 FROM V$log_history
 group by trunc(first_time), to_char(first_time, 'Dy')
 Order by 1

Useful scripts: Catch a session, causing ‘cursor: pin S wait on X’…

For sure, every network from time to time aborts connection. Especially this commonly could be seen in WANs.

When this happens while a session is fetching data or using some other object through db-link, PMON for some reason (from time to time) is unable to kill this session, so session stucks, leading to ‘cursor: pin S wait on X’ wait event.

It’s quite difficult to find out, which session you need to kill to release memory lock, so here is the query for this:

SELECT *
 FROM v$session
 WHERE sid IN
 (SELECT TO_NUMBER (SUBSTR (TO_CHAR (RAWTOHEX (p2raw)), 1, 8),
 'XXXXXXXX') sid
 FROM v$session
 WHERE event = 'cursor: pin S wait on X')

The following screenshot shows reducing Latch/mutex waits:

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