重新挂载：
[root@localhost ~]# umount /dev/shm
[root@localhost ~]# mount /dev/shm
[root@localhost ~]# df -h /dev/shm
Filesystem Size Used Avail Use% Mounted on
tmpfs 1.0G 0 1.0G 0% /dev/shm
再次启动数据库
SQL> startup pfile='/home/oracle/initorcl.ora';
ORACLE instance started.
Total System Global Area 535662592 bytes
Fixed Size 1337720 bytes
Variable Size 327157384 bytes
Database Buffers 201326592 bytes
Redo Buffers 5840896 bytes
Database mounted.
Database opened.
SQL> show sga
Total System Global Area 535662592 bytes
Fixed Size 1337720 bytes
Variable Size 327157384 bytes
Database Buffers 201326592 bytes
Redo Buffers 5840896 bytes
SQL> select 535662592/1024/1024 from dual;
535662592/1024/1024
-------------------
510.847656
可 以看到已经修改过来了。
最后验证同步功能。