The oracle was working properly on the server but suddenly from 2 days ago I've not been able to connect it, unfortunately the server manager is not around for weeks and I am not familiar with oracle very much, I appreciate your help in advance.
The error:
An error was encountered performing the requested operation:
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
01034. 00000 - "ORACLE not available"
*Cause: Oracle was not started up. Possible causes include the following
- The SGA requires more space than was allocated for it.
- The operating-system variable pointing to the instance is
improperly defined.
*Action: Refer to accompanying messages for possible causes and correct
the problem mentioned in the other messages.
If Oracle has been initialized, then on some operating systems,
verify that Oracle was linked correctly. See the platform
specific Oracle documentation.
Vendor code 1034
The database has been stopped deliberately or it has crashed. No way to tell without consulting the alert log and any trace files which might have been generated.
This is not the sort of thing which can be talked through on SO. It requires genuine expertise, If you haven't got a DBA or anybody with power user access to the server you're out of luck.
Does this database matter? I'm tempted to say "obviously not", because who would leave a critical business process untended for "weeks"? However, if you really need this database you'll have to tell your boss they'll have to spring for an emergency DBA.