系统：centos 7.9 64位
数据库：oracle 11.2.0.4 64位
环境：rac(双节点) + dg
问题描述：dg端drop standby log报错ORA-00261、ORA-00312，如下所示：
SQL> select a.thread#,a.group#,b.member,b.type,a.bytes/1024/1024 MB from v$standby_log a,v$logfile b where a.group#=b.group#;
THREAD# GROUP# MEMBER TYPE MB
---------- ---------- ------------------------------------------------------------ ------- ----------
1 10 /u01/app/oracle/oradatastandby10.log STANDBY 50
1 10 /u01/app/oracle/oradatastandby10b.log STANDBY 50
1 11 /u01/app/oracle/oradatastandby11.log STANDBY 50
1 11 /u01/app/oracle/oradatastandby11b.log STANDBY 50
1 12 /u01/app/oracle/oradatastandby12.log STANDBY 50
1 12 /u01/app/oracle/oradatastandby12b.log STANDBY 50
2 13 /u01/app/oracle/oradatastandby13.log STANDBY 50
2 13 /u01/app/oracle/oradatastandby13b.log STANDBY 50
2 14 /u01/app/oracle/oradatastandby14.log STANDBY 50
2 14 /u01/app/oracle/oradatastandby14b.log STANDBY 50
2 15 /u01/app/oracle/oradatastandby15.log STANDBY 50
2 15 /u01/app/oracle/oradatastandby15b.log STANDBY 50
20 rows selected.
SQL> alter database drop logfile group 10;
alter database drop logfile group 10
*
ERROR at line 1:
ORA-00261: log 10 of thread 1 is being archived or modified
ORA-00312: online log 10 thread 1: '/u01/app/oracle/oradatastandby10.log'
ORA-00312: online log 10 thread 1: '/u01/app/oracle/oradatastandby10b.log'
异常原因：RFS进程未释放当前standby redo log文件.
解决过程：
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.
Total System Global Area 1586708480 bytes
Fixed Size 2253624 bytes
Variable Size 989859016 bytes
Database Buffers 587202560 bytes
Redo Buffers 7393280 bytes
Database mounted.
Database opened.
SQL> select open_mode from v$database;
OPEN_MODE
--------------------
READ ONLY
SQL> select process,status from v$managed_standby;
PROCESS STATUS
--------- ------------
ARCH CONNECTED
ARCH CONNECTED
ARCH CONNECTED
ARCH CONNECTED
SQL> alter database drop logfile group 10;
Database altered.
