How to connect to Oracle with ORA-00020: maximum number of processes

Connection to Oracle fails:

sqlplus /nolog

SQL*Plus: Release 11.2.0.4.0 Production on Fri Jun 6 09:07:23 2014
Copyright (c) 1982, 2013, Oracle.  All rights reserved.
@ SQL> connect /
ERROR:
ORA-00020: maximum number of processes (1000) exceeded

Solution: try connecting with --prelim option:

sqlplus -prelim "/ as sysdba"
SQL*Plus: Release 11.2.0.4.0 Production on Fri Jun 6 09:09:15 2014

Copyright (c) 1982, 2013, Oracle.  All rights reserved.
SQL> shutdown abort

in short, the -prelim option will not try to create private session structures in the SGA. This allows you to connect to perform debugging or shutdown operations.