手动修改Oracle sga方法有很多种，这里只介绍其中一种，就是用oracle debug工具     SQL> alter database open read only;

    Database altered.

    SQL> col scn for 9999999999999999     SQL> select dbms_flashback.get_system_change_number scn from dual;

                  SCN     —————–        10999733447365

    SQL> oradebug setmypid     Statement processed.     SQL>  oradebug DUMPvar SGA kcsgscn_     kcslf kcsgscn_ [060012658, 060012688) =  13346AC5 00000A01 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 60012338 00000000

    修改内存地址从0×060012658之后的4个字节，内容为0xffffffff     SQL> oradebug poke 0×060012658 4 0xffffffff     BEFORE: [060012658, 06001265C) = 13346AC5     AFTER:  [060012658, 06001265C) = FFFFFFFF

    SQL> oradebug DUMPvar SGA kcsgscn_     kcslf kcsgscn_ [060012658, 060012688) =  FFFFFFFF 00000A01 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 60012338 00000000

    可以看到已经修改成功     SQL> select dbms_flashback.get_system_change_number scn from dual;

                  SCN     —————–        11003706212351            SQL> select current_scn scn from v$database;

                  SCN     —————–                     0