sqlplus -prelim

If all the available processes in a database are used up, you will get an ORA-00020 when you try to login. The best way round this is to get some people to log out. However, this may not be possible e.g. if people have logged in from some application then killed it, leaving their sessions alive in the database but with no way to get back to them and end them tidily.

 

Oracle 11: sqlplus / as sysdba

 

SQL*Plus: Release 11.2.0.1.0 Production on Wed Nov 13 15:56:40 2013

 

Copyright (c) 1982, 2009, Oracle.  All rights reserved.

 

ERROR:

ORA-00020: maximum number of processes (100) exceeded

 

Enter user-name: ^C

Oracle 11:

 

An alternative is to login with the –prelim option. This does not allow you to run any SQL but it does let you close the database:

 

Oracle 11: sqlplus -prelim / as sysdba

 

SQL*Plus: Release 11.2.0.1.0 Production on Wed Nov 13 15:56:59 2013

 

Copyright (c) 1982, 2009, Oracle.  All rights reserved.

 

SQL> select sysdate from dual;

select sysdate from dual

*

ERROR at line 1:

ORA-01012: not logged on

Process ID: 0

Session ID: 0 Serial number: 0

 

SQL> shutdown abort

ORACLE instance shut down.

SQL>

Before opening the database again, you might consider increasing the processes parameter to reduce the chance of this happening again.

Server Parameter Files

This was tested on Oracle 11.2. Some initialisation parameters cannot be changed while the database is open. If you try to change one of these, you get an ORA-02095:

 

SQL> alter system set sessions = 30;

alter system set sessions = 30

                 *

ERROR at line 1:

ORA-02095: specified initialization parameter cannot be modified

 

SQL>

 

If you are using a server parameter file, you can make the change there and bounce the database. But if you are not then this option is not available to you either:

 

SQL> l

  1  alter system set sessions = 30

  2* scope = spfile

SQL> /

alter system set sessions = 30

*

ERROR at line 1:

ORA-32001: write to SPFILE requested but no SPFILE is in use

 

SQL>

 

You can start using a server parameter file as follows. This assumes that the database is a test one and nobody else is using it. Otherwise you should check with the users first then do a shutdown normal to bounce the database instead:

 

SQL> create spfile from pfile;

 

File created.

 

SQL> startup force;

ORACLE instance started.

 

Total System Global Area  417669120 bytes

Fixed Size                  2148672 bytes

Variable Size             255858368 bytes

Database Buffers          155189248 bytes

Redo Buffers                4472832 bytes

Database mounted.

Database opened.

SQL>

 

Then you can make the change which failed above:

 

SQL> alter system set sessions = 30

  2  scope = spfile;

 

System altered.

 

SQL> startup force

ORACLE instance started.

 

Total System Global Area  417669120 bytes

Fixed Size                  2148672 bytes

Variable Size             260052672 bytes

Database Buffers          150994944 bytes

Redo Buffers                4472832 bytes

Database mounted.

Database opened.

SQL>

 

I will look at server parameter files in more detail in a future post but I wanted to show you this as it happened to me today. You may wonder why I set the sessions parameter so low. I did it on purpose to demonstrate ORA-00018. Unfortunately, the change did not work:

 

SQL> l

  1  select value from v$parameter

  2* where name = 'sessions'

SQL> /

 

VALUE

----------

776

 

SQL>

 

I checked the Oracle 11.2 documentation on this and it said that the minimum value allowed for the sessions parameter is processes * 1.5 + 22. The processes parameter for this database is set to 500:

 

SQL> l

  1  select value from v$parameter

  2* where name = 'processes'

SQL> /

 

VALUE

----------

500

 

SQL>

 

This should give me a sessions value of 500 + 250 + 22 = 772 so it is not too far out. I'll just have to think of another way to demonstrate ORA-00018!