ORA-27101: shared memory realm does not exist

SQL*Plus: Release 9.2.0.1.0 - Production on Sat Aug 11 03:12:33 2007

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ERROR:
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist

Solution :

sqlplus /nolog

Uma vez no sqlplus, veja a minha sessão abaixo :

SQL> connect / as sysdba
Connected to an idle instance.
SQL> startup
ORACLE instance started.

Total System Global Area 126950220 bytes
Fixed Size 453452 bytes
Variable Size 109051904 bytes
Database Buffers 16777216 bytes
Redo Buffers 667648 bytes
Database mounted.
Database opened.
SQL> quit

A partir daqui a instancia volta a funcionar !