练习环境： LINUX（Centos8) +ORACL 12C2R
启动ORACLE 数据库，出现下面错误信息内容。
ORA-01113: file 9 needs media recovery解决
问题：
SQL> startup
ORACLE instance started.
Total System Global Area 1610612736 bytes
Fixed Size 779080 bytes
Variable Size 535043256 bytes
Database Buffers 1073741824 bytes
Redo Buffers 1048576 bytes
Database mounted.
ORA-01113: file 9 needs media recovery
ORA-01110: data file 9: '/u01/app/oracle/oradata/orcl/orclpdb/system01.dbf'
解决方法：
[oracle#ora12c ~]$ sqlplus sys/ as sysdba 我的密码
SQL> RECOVER DATAFILE '/u01/app/oracle/oradata/orcl/orclpdb/system01.dbf'
Media recovery complete.
SQL> recover tablespace system;
Media recovery complete.
SQL> RECOVER DATABASE;
Media recovery complete.
SQL> ALTER DATABASE OPEN;
Database altered.