ORA-01624: log 3 needed for crash recovery of instance orcl (thread 1)

SQL> select  GROUP#, STATUS, TYPE, MEMBER from v$logfile;

    GROUP# STATUS  TYPE
---------- ------- -------
MEMBER
--------------------------------------------------------------------------------
  3    ONLINE
/u01/app/oracle/oradata/ORCL/onlinelog/o1_mf_3_dyd9t6b2_.log

  3    ONLINE
/u01/app/oracle/fast_recovery_area/ORCL/onlinelog/o1_mf_3_dyd9tcwo_.log

  2    ONLINE
/u01/app/oracle/oradata/ORCL/onlinelog/o1_mf_2_dyd9sokw_.log

    GROUP# STATUS  TYPE
---------- ------- -------
MEMBER
--------------------------------------------------------------------------------
  2    ONLINE
/u01/app/oracle/fast_recovery_area/ORCL/onlinelog/o1_mf_2_dyd9stxc_.log

  1    ONLINE
/u01/app/oracle/oradata/ORCL/onlinelog/o1_mf_1_dycmddnl_.log

  1    ONLINE
/u01/app/oracle/fast_recovery_area/ORCL/onlinelog/o1_mf_1_dycmdlh3_.log

    GROUP# STATUS  TYPE
---------- ------- -------
MEMBER
--------------------------------------------------------------------------------
  4    ONLINE
/data/oracle/onlinelog/REDO04a.LOG

  4    ONLINE
/data/oracle/onlinelog/REDO04b.LOG

  5    ONLINE
/data/oracle/onlinelog/REDO05a.LOG

    GROUP# STATUS  TYPE
---------- ------- -------
MEMBER
--------------------------------------------------------------------------------
  5    ONLINE
/data/oracle/onlinelog/REDO05b.LOG

  6    ONLINE
/data/oracle/onlinelog/REDO06a.LOG

  6    ONLINE
/data/oracle/onlinelog/REDO06b.LOG

12 rows selected.

SQL>
SQL> alter database drop logfile group 1;

Database altered.

SQL> alter database drop logfile group 2;

Database altered.

SQL> alter database drop logfile group 3;
alter database drop logfile group 3
*
ERROR at line 1:
ORA-01623: log 3 is current log for instance orcl (thread 1) - cannot drop
ORA-00312: online log 3 thread 1:
'/u01/app/oracle/oradata/ORCL/onlinelog/o1_mf_3_dyd9t6b2_.log'
ORA-00312: online log 3 thread 1:
'/u01/app/oracle/fast_recovery_area/ORCL/onlinelog/o1_mf_3_dyd9tcwo_.log'

SQL> select GROUP#,members,BYTES/1024/1024 size_M,STATUS,ARCHIVED from v$log;

    GROUP#    MEMBERS   SIZE_M STATUS    ARC
---------- ---------- ---------- ---------------- ---
  3     2      500 CURRENT   NO
  4     2     1024 UNUSED    YES
  5     2     1024 UNUSED    YES
  6     2     1024 UNUSED    YES

SQL> alter system switch logfile;

System altered.

SQL> select GROUP#,members,BYTES/1024/1024 size_M,STATUS,ARCHIVED from v$log;

    GROUP#    MEMBERS   SIZE_M STATUS    ARC
---------- ---------- ---------- ---------------- ---
  3     2      500 ACTIVE    YES
  4     2     1024 CURRENT   NO
  5     2     1024 UNUSED    YES
  6     2     1024 UNUSED    YES

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 orcl (thread 1)
ORA-00312: online log 3 thread 1:
'/u01/app/oracle/oradata/ORCL/onlinelog/o1_mf_3_dyd9t6b2_.log'
ORA-00312: online log 3 thread 1:
'/u01/app/oracle/fast_recovery_area/ORCL/onlinelog/o1_mf_3_dyd9tcwo_.log'

SQL> alter system checkpoint;

System altered.

SQL> select GROUP#,members,BYTES/1024/1024 size_M,STATUS,ARCHIVED from v$log;

    GROUP#    MEMBERS   SIZE_M STATUS    ARC
---------- ---------- ---------- ---------------- ---
  3     2      500 INACTIVE   YES
  4     2     1024 CURRENT   NO
  5     2     1024 UNUSED    YES
  6     2     1024 UNUSED    YES

SQL> alter database drop logfile group 3;

Database altered.

SQL> alter system switch logfile;

System altered.

SQL> select GROUP#,members,BYTES/1024/1024 size_M,STATUS,ARCHIVED from v$log;

    GROUP#    MEMBERS   SIZE_M STATUS    ARC
---------- ---------- ---------- ---------------- ---
  4     2     1024 ACTIVE    YES
  5     2     1024 CURRENT   NO
  6     2     1024 UNUSED    YES

SQL> select member from v$logfile;

MEMBER
--------------------------------------------------------------------------------
/data/oracle/onlinelog/REDO04a.LOG
/data/oracle/onlinelog/REDO04b.LOG
/data/oracle/onlinelog/REDO05a.LOG
/data/oracle/onlinelog/REDO05b.LOG
/data/oracle/onlinelog/REDO06a.LOG
/data/oracle/onlinelog/REDO06b.LOG

6 rows selected.