sqlplus not connecting as "/ AS SYSDBA" - oracle

Question

I installed oracle database express edition 18c. I'm using windows 10.
when I execute "/ AS SYSDBA" in sqlplus to user-name, it gives the following error.
ERROR:
ORA-28056: Writing audit records to Windows Event Log failed
ORA-28056: Writing audit records to Windows Event Log failed
when I execute below
Enter user-name: SYS AS SYSDBA
Enter password: <password I gave on installation>
it prints below error
ERROR:
ORA-28056: Writing audit records to Windows Event Log failed
OSD-32765: Message 32765 not found; product=RDBMS; facility=SOSD
O/S-Error: (OS 5) Access is denied.
ORA-28056: Writing audit records to Windows Event Log failed
OSD-32765: Message 32765 not found; product=RDBMS; facility=SOSD
O/S-Error: (OS 5) Access is denied.
when I try to execute below
Enter user-name: SYSTEM
Enter password: <password I gave on installation>
it prints below error
ERROR: ORA-01034: ORACLE not available ORA-27101: shared
memory realm does not exist Process ID: 0 Session ID: 0
Serial number: 0
So how can I connect to the database?
Note: I cleared all the event logs from event viewer. not worked!!
Additionally by default there are no environment variable set. so I set
set ORACLE_HOME=C:\app\user\product\18.0.0\dbhomeXE
set ORACLE_SID=CLRExtProc
After setting above it provides below error
ERROR:
ORA-12560: TNS:protocol adapter error
so please help me to connect to database
Thank you!!!

Answer 1

Probably you have not configured properly the sqlnet.ora file
Try to run this
C:\>sqlplus / as sysdba
SQL*Plus: Release 18.0.0.0.0 - Production on Wed Aug 26 15:49:17 2020
Version 18.4.0.0.0
Copyright (c) 1982, 2018, Oracle. All rights reserved.
ERROR:
ORA-01017: invalid username/password; logon denied
If you get this error, then open the SQLNET.ORA file and edit the following parameter AUTHENTICATION_SERVICES value to NTS. Save it.
SQLNET.AUTHENTICATION_SERVICES= (NONE)
to
SQLNET.AUTHENTICATION_SERVICES= (NTS)
Try again and it should work, as long as the windows service is running. Don't forget to set the ORACLE_SID environment variable
set ORACLE_SID=sid
Where sid is the name of the database you want to connect to. Finally
C:\>sqlplus / as sysdba
SQL*Plus: Release 18.0.0.0.0 - Production on Wed Aug 26 15:49:34 2020
Version 18.4.0.0.0
Copyright (c) 1982, 2018, Oracle. All rights reserved.
Connected to:
Oracle Database 18c Express Edition Release 18.0.0.0.0 - Production
Version 18.4.0.0.0
SQL>
Update
The database can't write into the Windows Event Log.
Open Event Viewer, click Start, click Control Panel, click Performance and Maintenance, click Administrative Tools, and then double-click Event Viewer. You must be logged on as an administrator or a member of the Administrators group to free an event log.
Then use any of the next options:
When a log is full, it stops recording new events. Clearing the log is one way to free the log and start recording new events. You can also free a log and start recording new events by overwriting old events. To overwrite events, on the Action menu, click Properties, and then click Overwrite events as needed. This ensures that all new events are written to the log, even when the log is full.
You can also start logging new events by increasing the maximum log size. To increase the log size, on the Action menu, click Properties, and then increase the Maximum log size.