_single_process Initialization Parameter

The _single_process initialization parameter allows you to start an instance in single process mode. As it begins with an underscore, you should only use it when Oracle tell you to. When I tried it on Oracle 10 and Oracle 11 test databases, they promptly fell over. However, I was able to get it to work on Oracle 9, although it produced an ORA-00600. I then left the SYSDBA session open: 

Oracle 9: sqlplus '/ as sysdba'

 

SQL*Plus: Release 9.2.0.7.0 - Production on Mon Nov 11 18:49:19 2013

 

Copyright (c) 1982, 2002, Oracle Corporation.  All rights reserved.

 

Connected to an idle instance.

 

SQL> startup

ORACLE instance started.

 

Total System Global Area  106139816 bytes

Fixed Size                   733352 bytes

Variable Size              75497472 bytes

Database Buffers           29360128 bytes

Redo Buffers                 548864 bytes

ORA-00600: internal error code, arguments: [ksfdgfnm1], [0x40228B858], [], [],

[], [], [], []

 

SQL> col value format a30

SQL> select value from v$parameter

  2  where name = '_single_process'

  3  /

 

VALUE

------------------------------

TRUE

 

SQL> 

… and a subsequent login attempt from another server session failed with an ORA-00024: 

Oracle 9: sqlplus /

 

SQL*Plus: Release 9.2.0.7.0 - Production on Mon Nov 11 18:36:55 2013

 

Copyright (c) 1982, 2002, Oracle Corporation.  All rights reserved.

 

ERROR:

ORA-00024: logins from more than one process not allowed in single-process mode

 

Enter user-name: