oracle error- ORA-00306: limit of string instances in this database

ORA-00306:	limit of string instances in this database
Cause:	Starting this instance would exceed the maximum number of instances allowed for this database. This message occurs only with STARTUP shared and multiple instances.
Action:	You cannot start more than the lower of a) port-specific limit as to the number of instances b) the number of instances specified at create-database time

oracle error -- ORA-00305: log string of thread string inconsistent; belongs to another database

ORA-00305:	log string of thread string inconsistent; belongs to another database
Cause:	The database ID in the redo log file does not match the database ID in the control file. This redo log file is not from the current database.
Action:	Specify the correct redo log file, then retry the operation.

ORA-00304:	requested INSTANCE_NUMBER is busy
Cause:	An instance tried to start by using a value of the initialization parameter INSTANCE_NUMBER that is already in use.
Action:	Either a) specify another INSTANCE_NUMBER, b) shut down the running instance with this number c) wait for instance recovery to complete on the instance with this number.