Getting the following error in Oracle Dataguard Standby server when going to switch for readonly mode to test and rollback with help of flashback command

476108 24-OCT-2025 08:42:44 Errors in file E:\ORACLE\diag\rdbms\dr\dr\trace\dr_mz00_8728.trc:
ORA-00313: open failed for members of log group 6 of thread 1 
ORA-00312: online log 6 thread 1: 'E:\FLASHBACK\DR\ONLINELOG\O1_MF_6_NG3MZQJ1_.LOG' 
ORA-27041: unable to open file 
OSD-04002: unable to open file O/S-Error: (OS 2) The system cannot find the file specified. 476114 
24-OCT-2025 08:48:27

Possible Causes

• The log file 'E:\FLASHBACK\DR\ONLINELOG\O1_MF_6_NG3MZQJ1_.LOG' might have been deleted, moved, or corrupted.
• The disk or mount point may be inaccessible.
• A recent restore or DR activity might have missed this file.

Cause: On checking the file is not present in the E:\FLASHBACK\DR location

Solution:

1. Check the log file members and location:

SELECT GROUP#, STATUS, MEMBER FROM V$LOGFILE;
SELECT GROUP#, THREAD#, SEQUENCE#, STATUS FROM V$LOG;

2. Clear the log group which causing issue

 ALTER DATABASE CLEAR LOGFILE GROUP 6;

3. On clearing the log group, my problem is resolved. The alter command will work.