How to rename a database to use lower case instead of upper case characters

At my customer's site, we have standardized the Oracle SIDs (System ID) to use lower case character.

During an upgrade, the SID was accidently set to upper case. This new uppercase SID was picked up by Oracle Cloud Control and all of a sudden we had a non-standardized database within our ranks. Not a disaster, but irritating, nevertheless.

Given that your environment variable in you operating system is also set to lower case, you can simply restart the database with a new value for the parameter db_name in the parameter file to rectify the situation. There is no need to use the nid ("new id") tool or to recreate the controlfile. A simple restart with the right value for the parameter db_name will do.

It's easy to verify this conclution if you have access to another database which adheres to the standard. Check the value of the columnn name in v$database:

select name from v$database;

NAME
---------
PRODDB01

SQL> show parameter db_name

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
db_name                              string      PRODDB01

As expected, the query from v$database it is displayed in upper case as Oracle alwaysd does by default, but we also see that the value of the parameter db_name is actually in lower case.

In other words, there is no connection between the value of ORACLE_SID and the name of the database used in the controlfile. Oracle will always refer to the database in upper case. How we present and use this value in the operating system, is up to us.

These are the simple steps to get the value of the db_name parameter aligned with the value of your operating system variable ORACLE_SID:

Check your environment variable:

env | grep ORA
ORACLE_SID=testdb01 

It is indeed shown in lower case

Create a new pfile:

sqlplus / as sysdba
create pfile='inittestdb01.ora' from spfile;

Edit the pfile so that the db_name parameter has its value in lower case:

Old value:
*.db_name='TESTDB01'

New value:

*.db_name='testdb01'

Restart the database:

sqlplus / as sysdba
shutdown immediate
startup

If desirable, create a new spfile and restart the database one final time to instruct oracle to use it instead of the pfile:

create spfile from pfile='inittestdb01.ora';
shutdown immediate
startup