Total System Global Area 1577054672 bytes
Fixed Size 8896976 bytes
Variable Size 385875968 bytes
Database Buffers 1174405120 bytes
Redo Buffers 7876608 bytes
Database mounted.
ORA-16649: possible failover to another database prevents this database from
being opened
去掉DG相关配置，包含LOG_ARCHIVE_CONFIG，DG BROKER 等。再次打开数据库
SYS@PROD5> alter database open;
alter database open
*
ERROR at line 1:
ORA-03113: end-of-file on communication channel
Process ID: 15332
Session ID: 2 Serial number: 49488
检查报警文件：
见日志：
2023-08-23T23:18:12.715745+08:00
LGWR (PID:15299): Primary database is in MAXIMUM AVAILABILITY mode
LGWR (PID:15299): LAD:1 is not serviced by LGWR
LGWR (PID:15299): Minimum of one LGWR standby database required
说明是最大可用模式，但现在备库没有，所以直接关闭了。
下面解决办法，就是转换为最大性能模式即可
--重新启动到MOUNT
SYS@PROD5> conn / as sysdba
Connected to an idle instance.
SYS@PROD5> startup mount;
SYS@PROD5> select name,PROTECTION_MODE ,PROTECTION_LEVEL from v$database;
NAME PROTECTION_MODE PROTECTION_LEVEL
--------- -------------------- --------------------
PROD5 MAXIMUM AVAILABILITY UNPROTECTED
SYS@PROD5> alter database set standby database to maximize performance;
Database altered.
SYS@PROD5> select name,PROTECTION_MODE ,PROTECTION_LEVEL from v$database;
NAME PROTECTION_MODE PROTECTION_LEVEL
--------- -------------------- --------------------
PROD5 MAXIMUM PERFORMANCE UNPROTECTED