ORA-00304: requested INSTANCE_NUMBER is busy due to db_unique_name parameter and Startup Oracle Instance

Hi,

When I startup the new Oracle Instance,  I got ” ORA-00304: requested INSTANCE_NUMBER is busy ” error.

Details of error are as follows.

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.

[NEWDB]/home/oracle $ . NEWDB_profile 
[NEWDB]/home/oracle $ sqlplus / as sysdba            

SQL*Plus: Release 18.0.0.0.0 - Production on Fri Jun 19 23:14:04 2020
Version 18.3.0.0.0

Copyright (c) 1982, 2018, Oracle.  All rights reserved.

Connected to an idle instance.

SQL> startup nomount pfile='/home/oracle/initNEWDB.ora';
ORA-00304: requested INSTANCE_NUMBER is busy
SQL> exit
Disconnected
[NEWDB]/home/oracle $

This error is related with the same Database Name or Instance name on Same Server.

To solve this problem, You should check if same Instance name exist on same Server or not.

If the same Instance name exist on same server, then rename the new Instance name or DB Name.

*.db_unique_name=’NEWDB’

I would restore the existing database at the same server from backup with different instance name, To solve this error you should use the db_unique_name parameter in the parameter ( spfile, pfile ) file as follows.

[NEWDB]/home/oracle $ cat initNEWDB.ora 
*.audit_file_dest='/u01/app/oracle/admin/NEWDB/adump'
*.audit_trail='DB'
*.cluster_database=false
*.compatible='18.3.0'
*.control_files='+DATATEST/NEWDB/controlfile/control01.ctl'
*.core_dump_dest='/u01/app/oracle/diag/rdbms/NEWDB/NEWDB/cdump'
*.db_block_size=8192
*.db_domain=''
*.db_name='MSDB'
*.db_unique_name='NEWDB'
*.db_recovery_file_dest_size=2147483648000
*.db_recovery_file_dest='+DATATEST'
*.dispatchers='(PROTOCOL=TCP) (SERVICE=NEWDBXDB)'
*.local_listener='LISTENER_NEWDB'
*.optimizer_mode='ALL_ROWS'
*.processes=300
*.result_cache_max_size=52448K
*.sga_target=10G
[NEWDB]/home/oracle $

Now try again, it will be solved.

[NEWDB]/home/oracle $ . NEWDB_profile 
[NEWDB]/home/oracle $ sqlplus / as sysdba 

SQL*Plus: Release 18.0.0.0.0 - Production on Fri Jun 19 23:16:23 2020
Version 18.3.0.0.0

Copyright (c) 1982, 2018, Oracle. All rights reserved.

Connected to an idle instance.

SQL> startup nomount pfile='/home/oracle/initNEWDB.ora';
ORACLE instance started.

Total System Global Area 1.0737E+10 bytes
Fixed Size 12207952 bytes
Variable Size 2717908992 bytes
Database Buffers 7952400384 bytes
Redo Buffers 54898688 bytes
SQL> exit
Disconnected from Oracle Database 18c Enterprise Edition Release 18.0.0.0.0 - Production
Version 18.3.0.0.0
[NEWDB]/home/oracle $

Do you want to learn Oracle Database for Beginners, then read the following articles.

https://ittutorial.org/oracle-database-19c-tutorials-for-beginners/