ORA-01624 error handling-Alter system checkpoint

SQL> alter database drop logfile group 2;
Alter database drop logfile Group 2
*
Error at line 1:
ORA-01624: log 2 needed for crash recovery of instance dbstat (thread 1)
ORA-00312: Online log 2 thread 1: '/data1/dbstat/redo2.log'

SQL> alter system switch logfile;

System altered.

SQL> select * from V $ log;

Group # thread # sequence # bytes members arc status first_change # first_time
-----------------------------------------------------------------------------------------------------
1 1 12 2147483648 1 no active 203704 19:04:23
2 1 11 52428800 1 no active 203206 18:56:08
3 1 13 2147483648 1 no current 203710 19:04:38
SQL>Alter system checkpoint;

System altered.

SQL> select * from V $ log;

Group # thread # sequence # bytes members arc status first_change # first_time
-----------------------------------------------------------------------------------------------------
1 1 12 2147483648 1 No inactive 203704 19:04:23
2 1 11 52428800 1 No inactive 203206 18:56:08
3 1 13 2147483648 1 no current 203710 19:04:38

SQL> alter database drop logfile group 2;

Database altered.

 

Checkpoint: The ckpt process triggers Oracle to perform the checkpoint action and writes dirty blocks in the data buffer (records have been written in redo but not written to datafile) the contents are written to the data file and the site space is released. It is completed by the dbw background process and the SCN of controlfile and datafile is modified.
Generally, manual execution is performed to delete a log but the log does not have content synchronized to the data file. You need to manually check the point to synchronize the data, and then you can drop the logfile group N.