用exp导出文件提示如下错误
exp er/er@ddd file=/root/temp/er.dmp tables=(db1)
Export: Release 9.2.0.7.0 - Production on Tue Jul 5 17:45:14 2011
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EXP-00056: ORACLE error 12535 encountered
ORA-12535: TNS:operation timed out
EXP-00000: Export terminated unsuccessfully