What is the query to find the number of current open cursors in an Oracle Instance?
Also, what is the accuracy/update frequency of this data?
I am using Oracle 10gR2
Total cursors open, by session:
select a.value, s.username, s.sid, s.serial#
from v$sesstat a, v$statname b, v$session s
where a.statistic# = b.statistic# and s.sid=a.sid
and b.name = 'opened cursors current';
Source: http://www.orafaq.com/node/758
As far as I know queries on v$ views are based on pseudo-tables ("x$" tables) that point directly to the relevant portions of the SGA, so you can't get more accurate than that; however this also means that it is point-in-time (i.e. dirty read).
select sql_text, count(*) as "OPEN CURSORS", user_name from v$open_cursor
group by sql_text, user_name order by count(*) desc;
appears to work for me.
Here's how to find open cursors that have been parsed. You need to be logged in as a user with access to v$open_cursor and v$session.
COLUMN USER_NAME FORMAT A15
SELECT s.machine, oc.user_name, oc.sql_text, count(1)
FROM v$open_cursor oc, v$session s
WHERE oc.sid = s.sid
GROUP BY user_name, sql_text, machine
HAVING COUNT(1) > 2
ORDER BY count(1) DESC
;
If gives you part of the SQL text so it can be useful for identifying leaky applications. If a cursor has not been parsed, then it does not appear here. Note that Oralce will sometimes keep things open longer than you do.
1)your id should have sys dba access
2)
select sum(a.value) total_cur, avg(a.value) avg_cur, max(a.value) max_cur,
s.username, s.machine
from v$sesstat a, v$statname b, v$session s
where a.statistic# = b.statistic# and s.sid=a.sid
and b.name = 'opened cursors current'
group by s.username, s.machine
order by 1 desc;
Oracle has a page for this issue with SQL and trouble shooting suggestions.
"Troubleshooting Open Cursor Issues"
http://docs.oracle.com/cd/E40329_01/admin.1112/e27149/cursor.htm#OMADM5352
I use something like this:
select
user_name,
count(*) as "OPEN CURSORS"
from
v$open_cursor
group by
user_name;
This could work:
SELECT sql_text "SQL Query",
Count(*) AS "Open Cursors"
FROM v$open_cursor
GROUP BY sql_text
HAVING Count(*) > 2
ORDER BY Count(*) DESC;
I would use this quick SQL to compare the highest current use compared to the max allowed. This will allow you to immediately see if any process has a dangerously high use of cursors.
SELECT MAX (a.VALUE) AS highest_open_cur, p.VALUE AS max_open_cur
FROM v$sesstat a, v$statname b, v$parameter p
WHERE a.statistic# = b.statistic#
AND b.name = 'opened cursors current'
AND p.name = 'open_cursors'
GROUP BY p.VALUE;
As is probably clear from the above SQL, the OPEN_CURSORS value is an Oracle parameter and can be found at runtime like this.
SELECT * FROM v$parameter WHERE NAME = 'open_cursors';
You may need to be sysdba or equivalent to query the above tables.
Related
Is there any way to uniquely identify current session in GV$SESSION view in Oracle?
I've faced with the problem that the following query may return more than one row in case of Oracle RAC configuration:
SELECT SID, SERIAL#
FROM GV$SESSION
WHERE AUDSID = Sys_Context('USERENV', 'SESSIONID')
AND SID = Sys_Context('USERENV', 'SID');
Using V$MYSTAT is not an option either, because V$MYSTAT may not be accessible for the current session (for example when statistic is disabled).
Try this:
SELECT SID, SERIAL#
FROM V$SESSION
WHERE AUDSID = Sys_Context('USERENV', 'SESSIONID');
Since you're interested in current session, the current session must be on the local instance (by definition), so use V$SESSION instead of GV$SESSION. Also, all you need is AUDSID to uniquely identify your session.
If you've got some reason you really need to use GV$SESSION (can't imagine why that would be), you could do this instead:
SELECT SID, SERIAL#
FROM GV$SESSION
WHERE AUDSID = Sys_Context('USERENV', 'SESSIONID')
AND INST_ID = USERENV('Instance');
Also, an alternate way to get the SID of the current session is:
select sid from v$mystat where rownum=1;
Hope that helps.
Joining gv$session and v$mystat :)
SELECT SID, SERIAL#,inst_id
FROM GV$SESSION
WHERE sid=(select sid from v$mystat where rownum=1);
Use V$SESSION instead of GV$SESSION
SELECT SID, SERIAL#
FROM V$SESSION
WHERE SID = Sys_Context('USERENV', 'SID');
Try this (will need access to v$session and v$sql views) -
select /*My Sess*/ 'My Sess Text = hello world # '||systimestamp SID_SR_TXT from dual
union
select 'SID = '||sid||' Serial# = '||serial# SID_SR_TXT from v$session where sql_id in
(select sql_id from v$sql where sql_text like '% My Sess %');
I use query:
select LAST_LOAD_TIME, ELAPSED_TIME, MODULE, SQL_TEXT elasped from v$sql
WHERE MODULE='JDBC Thin Client'
ORDER BY LAST_LOAD_TIME DESC
elasped:
delete from tableA where fk in (select pk from tableB where tableB.fk=:1
and tableB.date between :2 and :3)
Is it possible find these parameters 1, 2 and 3?
Something like this:
select s.sql_id,
bc.position,
bc.value_string,
s.last_load_time,
bc.last_captured
from v$sql s
left join v$sql_bind_capture bc
on bc.sql_id = s.sql_id
and bc.child_number = s.child_number
where s.sql_text like 'delete from tableA where fk%' -- or any other method to identify the SQL statement
order by s.sql_id, bc.position;
I have a co worker who wrote the following query. The first one works and the second one does not. Also if you remove the aggregate function from the subquery, it works. The oracle optimizer is doing something weird. Any thoughts? Running in SQL Developer 3.1 against 11.1.0.6.0 64 bit.
This works:
SELECT
a.fd_customer_key
, b.fd_customer_key
, b.counter
FROM FETCH_CUSTOMER a
, (select fd_customer_key, count(*) as counter from fetch_customer_order group by fd_customer_key) b
where a.fd_customer_key = b.fd_customer_key (+)
and b.counter is null
This doesn’t:
SELECT
a.fd_customer_key
, b.fd_customer_key
, b.counter
FROM FETCH_CUSTOMER a
, (select fd_customer_key, count(*) as counter from fetch_customer_order group by fd_customer_key) b
where a.fd_customer_key = b.fd_customer_key (+)
and b.fd_customer_key is null
Actually yes, both of the queries you provided are supposed to wrok the same way, but if i understand your need well, you are trying to select the fd_customer_key which has no Order?
I suggest the following query for your need, its more simple and less consuming :
SELECT a.fd_customer_key
FROM FETCH_CUSTOMER a
WHERE NOT EXISTS (SELECT 1
FROM fetch_customer_order b
WHERE a.fd_customer_key = b.fd_customer_key)
It seems like you are trying to make an anti-join (find the rows from FETCH_CUSTOMER that have no corresponding rows in FETCH_CUSTOMER_ORDER).
With Oracle you do not have to use this clever OUTER JOIN trick to write an anti-join, you could use a NOT IN or NOT EXISTS operator and let the optimizer find the best plan. This will be just as efficient and easier to read.
Anyway, I can't reproduce your findings, here's my setup:
CREATE TABLE a (ID NUMBER PRIMARY KEY);
CREATE TABLE b (a_id NUMBER NOT NULL, DATA VARCHAR2(30));
INSERT INTO a (SELECT object_id FROM all_objects);
INSERT INTO b (SELECT object_id, object_name
FROM all_objects WHERE object_type = 'VIEW');
SELECT a.id, b.a_id, b.cnt
FROM a, (SELECT a_id, COUNT(*) cnt FROM b GROUP BY a_id) b
WHERE a.id = b.a_id (+)
AND b.cnt IS NULL;
SELECT a.id, b.a_id, b.cnt
FROM a, (SELECT a_id, COUNT(*) cnt FROM b GROUP BY a_id) b
WHERE a.id = b.a_id (+)
AND b.a_id IS NULL;
You will find that both queries return rows. What is your DB version?
which column i need to use to join V$session and V$sqlarea?
My main aim is to find top 5 queries with most disk_reads and generate a report containing relevant information.
Thanks
Try below one, I think it satisfy your requirement.
Find top 5 queries with most disk_reads.
SELECT SESION.SID,
SESION.USERNAME,
OPTIMIZER_MODE,
HASH_VALUE,
ADDRESS,
CPU_TIME,
ELAPSED_TIME,
DISK_READS,
DIRECT_WRITES,
SQL_TEXT
FROM V$SQLAREA SQLAREA, V$SESSION SESION
WHERE SESION.SQL_HASH_VALUE = SQLAREA.HASH_VALUE
AND SESION.SQL_ADDRESS = SQLAREA.ADDRESS
AND SESION.USERNAME IS NOT NULL
AND ROWNUM < 6
ORDER BY DISK_READS DESC,ELAPSED_TIME DESC;
This SQL does the join:
select s.sid, s.serial#, a.sql_text
from v$session s
join v$sqlarea a on a.hash_value = s.sql_hash_value;
I'm looking for a way to find out if there are uncommited INSERT, UPDATE or DELETE statements in the current session. One way would be to check v$lock with the current sid, but that requires read access to v$lock, which is a problem if the DBA doesn't want to grant it. Any other ways (other than keeping track of all database commands issued by the application)?
you can check if your session has a row in V$TRANSACTION (obviously that requires read privilege on this view):
SQL> SELECT COUNT(*)
FROM v$transaction t, v$session s, v$mystat m
WHERE t.ses_addr = s.saddr
AND s.sid = m.sid
AND ROWNUM = 1;
COUNT(*)
----------
0
SQL> insert into a values (1);
1 row inserted
SQL> SELECT COUNT(*)
FROM v$transaction t, v$session s, v$mystat m
WHERE t.ses_addr = s.saddr
AND s.sid = m.sid
AND ROWNUM = 1;
COUNT(*)
----------
1
SQL> commit;
Commit complete
SQL> SELECT COUNT(*)
FROM v$transaction t, v$session s, v$mystat m
WHERE t.ses_addr = s.saddr
AND s.sid = m.sid
AND ROWNUM = 1;
COUNT(*)
----------
0
This is the query I normally use,
select s.sid
,s.serial#
,s.username
,s.machine
,s.status
,s.lockwait
,t.used_ublk
,t.used_urec
,t.start_time
from v$transaction t
inner join v$session s on t.addr = s.taddr;
SELECT * FROM V$TRANSACTION
WHERE STATUS='ACTIVE';
See:
http://forums.oracle.com/forums/thread.jspa?threadID=691061
Use the query below to find out pending transaction.
If it returns a value, it means there is a pending transaction.
Here is the query:
select dbms_transaction.step_id from dual;
References:
http://www.acehints.com/2011/07/how-to-check-pending-transaction-in.html
http://www.acehints.com/p/site-map.html
Also see...
How can I tell if I have uncommitted work in an Oracle transaction?
Matthew Watson can be modified to be used in RAC
select t.inst_id
,s.sid
,s.serial#
,s.username
,s.machine
,s.status
,s.lockwait
,t.used_ublk
,t.used_urec
,t.start_time
from gv$transaction t
inner join gv$session s on t.addr = s.taddr;
The easiest and most reliable solution is to try and start a transaction and see it if succeeds. If some code already started a transaction but has not yet issued any DML, then the V$TRANSACTION view won't show anything.
In this example below, I handle the exception to raise a user-defined application error. To defer to an existing exception handler, just do a SET TRANSACTION and then immediately COMMIT to undo it.
DECLARE
transaction_in_progress EXCEPTION;
PRAGMA EXCEPTION_INIT(transaction_in_progress, -1453);
BEGIN
SET TRANSACTION NAME 'CHECK_FOR_TRANSACTION_ALREADY_SET';
COMMIT; -- end transaction
EXCEPTION
WHEN transaction_in_progress THEN
RAISE_APPLICATION_ERROR(-20000,'Transaction is already in progress');
END;
/