ORA-01000: Maximum Open Cursors Exceeded

Once our client report that they are facing error  “ORA-01000: maximum open cursors exceeded” while  running a application . As it seems from error that the error is related to cursors limits i.e, open cursors are exceeding from it's defaults values. To solving this issue ,let's have a look on the open_cursor i.e, what is open_cursor and how it impact into  database.

Open cursors take up space in the shared pool, in the library cache. To keep a renegade session from filling up the library cache, or clogging the CPU with millions of parse requests, we set the parameter OPEN_CURSORS.

OPEN_CURSORS sets the maximum number of cursors each session can have open, per session. For example, if OPEN_CURSORS is set to 1000, then each session can have up to 1000 cursors open at one time. If a single session has OPEN_CURSORS # of cursors open, it will get an ora-1000 error when it tries to open one more cursor.

To solve this issue we can either increase the no. of open_cursors or kill the inactive session which has open the large number of cursors. Now we connect to the database and check the open_cursors limits :

C:\>sqlplus sys/xxxx@noida as sysdba
SQL*Plus: Release 11.2.0.1.0 Production on Fri Oct 14 18:05:30 2011
Copyright (c) 1982, 2010, Oracle.  All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> sho parameter open_cursors
NAME                          TYPE          VALUE
-----------------        ---------      -----------
open_cursors              integer            300

Since the no. of open_cursors is 300. So we list the top 10 sessions which are currently opening most cursors

SQL> select * from ( select ss.value, sn.name, ss.sid
 from v$sesstat ss, v$statname sn
 where ss.statistic# = sn.statistic#
 and sn.name like '%opened cursors current%'
 order by value desc) where rownum < 11 ;

VALUE           NAME                              SID
-----            -----------------                ----------
300         opened cursors current          131
300        opened cursors current          125
300        opened cursors current           143
300        opened cursors current          149
300        opened cursors current           17
300        opened cursors current           132
300        opened cursors current           23
300        opened cursors current           1
300        opened cursors current           9
300        opened cursors current          10
10 rows selected.

Now we check what make session 131 open to many cursors?

SQL>  select sid, status, event, seconds_in_wait state "wait(s)" , blocking_session "blk_sesn", prev_sql_id  "SQL_ID"  from v$session where sid=131;

SID  STATUS      EVENT                  WAIT(s)  STATE    BLK_SESN    SQL_ID
---   ----------   ------------------ --------     ---------   ---------    ---------------
131 INACTIVE rdbms ipc message   8745     WAITING                 6mqvntr9ytnga


Since the status of the cursor is INACTIVE so we can we kill the session by using the below command :

SQL> alter system kill session 'sid,serial#' immediate;

The other alternatives is to increase the no. of the open_cursors parameter as :

SQL> alter system set open_cursors=1500 scope=spfile;

In my case i have increased the values of the open_cursors and issue got solved.


Enjoy     :-) 

Open Standby in Read-write Mode When Primary is Lost

There may be scenario  where Primary database is lost and we are only left with the standby database . In this scenario's we have to open the standby database in read-write mode. Below are the steps to convert standby database to Primary database.

1.)  Open standby database in mount state : 
SQL> select name,open_mode from v$database;
NAME       OPEN_MODE
------     -------------
NOIDA      READ ONLY

SQL> shut immediate
Database closed.
Database dismounted.
ORACLE instance shut down.

SQL> startup mount
ORACLE instance started.
 
Total System Global Area      263639040  bytes
Fixed Size                             1373964      bytes
Variable Size                         230689012  bytes
Database Buffers                  25165824     bytes
Redo Buffers                        6410240       bytes
Database mounted.

SQL> select open_mode ,protection_mode , database_role from v$database ;
OPEN_MODE     PROTECTION_MODE           DATABASE_ROLE
---------        ----------------------       ----------------
MOUNTED       MAXIMUM PERFORMANCE    PHYSICAL STANDBY

2.) Recover if there is any archive logs:

SQL>recover standby database;
ORA-01153: an incompatible media recovery is active

To solve this issue, we cancel the media recovery by using the below command .

SQL> alter database recover managed standby database cancel;
Database altered.

SQL> recover standby database
ORA-00279: change 2698969 generated at 10/05/2011 16:46:58 needed for thread
ORA-00289: suggestion : D:\ARCHIVE\ARC0000000133_0761068614.0001
ORA-00280: change 2698969 for thread 1 is in sequence #133

Specify log: {<RET>=suggested | filename | AUTO | CANCEL}
cancel
Media recovery cancelled.

3.) Finish the Recovery process :  

The below command will perform the role transition as quickly as possible with little or no data loss and without rendering other standby databases unusable and to open the database in read-write mode we fire the below command : 

SQL>alter database recover managed standby database finish;
Database altered.

4.) Activate the Standby Database : 

SQL> alter database activate physical standby database ;
Database altered.

5.) Check the new status

SQL> select open_mode ,protection_mode , database_role from v$database ;

OPEN_MODE     PROTECTION_MODE           DATABASE_ROLE
---------         ----------------------      ---------------------
MOUNTED       MAXIMUM PERFORMANCE    PHYSICAL STANDBY

6.) Open the Database
SQL> alter database open ;
Database altered.

SQL> select open_mode ,protection_mode , database_role from v$database ;

OPEN_MODE       PROTECTION_MODE             DATABASE_ROLE
---------           ----------------------        --------------------
READ WRITE       MAXIMUM PERFORMANCE      PHYSICAL STANDBY

Enjoy   :-) 

Journeyman On OTN

Hello  All

It is a good day for me. Today i become the Journeyman on OTN site . It's great pleasure while being the journeyman . Working with Oracle is  exciting, challenging and great fun.

I am Passionate about Oracle.Though  i am working with oracle for few years and find that oracle is a great Database . whenever I ask a question to myself how much i know about oracle , the answer is  "NOTHING" . Now my aim is know "something" about oracle . There are lots to be learn and the journey is too long.

The only advise I will like to give others and try to follow myself is that always  work or choose the job that you are enthusiastic or  passionate about .If you are motivated or enthusiastic ,you will be able to learn more and enjoy while working . I beleive that knowledge is not only about learning but about sharing to others.

Enjoy    :-)