Check the CSA HealthReport and see if you see a correct date format and other settings. If not you may have to correct it. Sometimes it displays correctly even when not set properly.
Make sure the OS locale is set to US and database OS also set to US. Make sure the other NLS parameters are set accordingly as per Installation guide, especially NLS_TERRITORY.
If the issue is only with NLS_DATE_FORMAT, to resolve this, try the following solutions:
Basic reset of NLS_DATE_FORMAT:
1. Run the command:
alter system set nls_date_format='YYYY-MM-DD HH24:MI:SS' scope=spfile
2. Restart the database (the change requires a restart)
Advanced reset of NLS_DATE_FORMAT
0. create pfile from spfile;
1. Edit the pfile ora file and change this to
2. Then recreate the SPFILE.
- Edit the pfile
- Shutdown the instance
- Create spfile from pfile
- Startup the database