Oracle: unable to change to noarchivelog We discovered that our Oracle 12c database was taking up a large amount of disk space with archive logs, so I figured out how to delete the files, but I'm unable to disable archive logging.  We don't have an in-house DBA, so I'm trying to figure this out myself.  From lots of Googling, it's my understanding that I need to do the following:

sqlplus / as sysdba
shutdown immediate
startup mount
alter database noarchivelog;
alter database open;


I've got two problems though.  I can't do the "sqlplus / as sysdba", it complains about "ORA-12560: TNS:protocol adapter error" unless I specify the SID, even though it the environment variable is defined.  Also, when I do the shutdown, I get "ORA-12514: TNS:listener does not currently know of service requested in connect descriptor" and it disconnects me from Oracle.

C:\Users\administrator.MYDOMAIN&gt;set oracle_sid=orcm

C:\Users\administrator.MYDOMAIN&gt;sqlplus /nolog

SQL*Plus: Release 12.1.0.2.0 Production on Mon Feb 5 11:11:33 2018

Copyright (c) 1982, 2014, Oracle.  All rights reserved.

SQL&gt; connect / as sysdba
ERROR:
ORA-12560: TNS:protocol adapter error


SQL&gt; connect sys/password@orcm as sysdba
Connected.
SQL&gt;
SQL&gt;
SQL&gt; archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            E:\app\oracle\product\12.1.0\dbhome_1\RDBMS
Oldest online log sequence     6869
Next log sequence to archive   6871
Current log sequence           6871
SQL&gt; shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
ERROR:
ORA-12514: TNS:listener does not currently know of service requested in connect
descriptor


Warning: You are no longer connected to ORACLE.
SQL&gt;


Any assistance would be greatly appreciated.
ORA-12560: TNS:protocol adapter error on Windows is typically caused by incorrent ORACLE_HOME and ORACLE_SID environment variables.

Find the database service:



Find the path and name of the instance:



Based on that:

set ORACLE_HOME=O:\oracle\product\12.2.0\dbhome_1
set PATH=%ORACLE_HOME%\bin;%PATH%
set ORACLE_SID=RTG


Then try again:

sqlplus / as sysdba
shutdown immediate
startup mount
alter database noarchivelog;
alter database open;