there are some limitation with Export in Direct Mode : Direct=y If the table contains LOB type of columns , the direct mode can not be used. So I believe some sys tables have LOB columns so that the export is failed . You still can use export in conventional mode
解决方案 »
免费领取超大流量手机卡,每月29元包185G流量+100分钟通话, 中国电信官方发货