ORA-01624: log 3 needed for crash recovery of instance

SQL> select group#, status from v$log;

    GROUP# STATUS
---------- ----------------
         1 CURRENT
         2 ACTIVE
         3 ACTIVE
         4 ACTIVE

SQL> alter database drop logfile group 3;
alter database drop logfile group 3
*
ERROR at line 1:
ORA-01624: log 3 needed for crash recovery of instance XXXXXX(thread 1)
ORA-00312: online log 3 thread 1: '/u02/oradata/XXXX/XXXXX/redo03.log'

Easy problem to resolve. Simply perform a checkpoint on the database:

SQL> ALTER SYSTEM CHECKPOINT GLOBAL;

System altered.

SQL> select group#, status from v$log;

    GROUP# STATUS

---------- ----------------

         1 INACTIVE

         2 CURRENT

         3 INACTIVE

         4 INACTIVE

SQL> alter database drop logfile group 3;

Database altered.