ORA-00056: DDL lock on object string.string is already held in an incompatible mode
Cause: An attempt was made to acquire a DDL lock that is already locked.
Action: This happens if you attempt to drop a table that has parse locks on it.

ORA-00051: timeout occurred while waiting for a resource
Cause: Usually due to a dead instance.
Action: Check for any dead, unrecovered instances and recover them.

ORA-00038: Cannot create session: server group belongs to another user
Cause: An attempt was made to create a non-migratable session in a server group that is owned by a different user.
Action: A server group is owned by the first user who logs into a server in the server group in non-migratable mode. All subsequent non-migratable mode logins must be made by the user who owns the server group. To have a different user login in non-migratable mode, the ownership of the server group will have to be changed. This can be …

ORA-00200: control file could not be created
Cause: It was not possible to create the control file.
Action: Check that there is sufficient disk space and no conflicts in filenames and try to create the control file again.

ORA-00087: command cannot be executed on remote instance
Cause: Cluster database command issued for non cluster database ORADEBUG command.
Action: Issue the command without the cluster database syntax.

ORA-00082: memory size of string is not in valid set of [1], [2], [4]stringstringstringstringstring
Cause: An invalid length was specified for the POKE command.
Action: Use a valid length (either 1, 2, 4, or possibly 8).

ORA-00077: dump string is not valid
Cause: An attempt was made to invoke an invalid dump.
Action: Try another dump.

ORA-00072: process “string” is not active
Cause: An invalid process was specified.
Action: Specify a valid process.

ORA-00067: invalid value string for parameter string; must be at least string
Cause: The value for the initialization parameter is invalid.
Action: Choose a value as indicated by the message.

ORA-00062: DML full-table lock cannot be acquired; DML_LOCKS is 0
Cause: The instance was started with DML_LOCKS = 0, and the statement being executed needs a full-table lock (S, X, or SSX).
Action: Restart the instance with DML_LOCKS not equal to zero, and reexecute the statement.