昨天实验备份，顺便记录下来。执行：
expdp user/pass directory=backup dumpfile=cc.dmp logfile=backup.log
提示
ORA-39002: invalid operation
ORA-39070: Unable to open the log file.
ORA-39087: directory name backup is invalid
google发现要建立对应的目录，使用sqlplus登陆，执行：
create directory backup as '/home/oracle/backup';
grant read, write on directory backup to user;
这样就可以正常运行expdp了，expdp备份确实快。
