▲这个错误是如何产生的?

[xxiao07]

Select NFINLST.TRXCODE,NFINLST.ZONENO,NFINLST.ACTBRNO,NFINLST.BUSIDATE
From ADIT.NFINLST@ORA151,ADIT.NFBALAN@ORA151
Where rownum<=8000 and ( NFINLST.ACCNO like '12%' and NFINLST.DRCRF = '2' and NFINLST.AMOUNT >= 10000000 AND..........)
做了以上查询，一般10分钟过了可以有结果，这次过很长时间（2个小时）才出来以下错误：
---------------------------------------------------------------------------------
ORA-01555: snapshot too old: rollback segment number 9 with name "RBS8" too small
ORA-02063: 紧接着line（源于ORA151）
----------------------------------------------------------------------------------

请大家分析一下，是什么原因产生了这个错误?
谢谢！

[xxiao07]

为什么“"RBS8" too small”？

[bobfang]

这是因为你查询的表在查询期间已被修改，并且保存修改前的数据的回滚段已被其他事务使用，所以oracle无法读取修改前的数据了。

[qiaozhiwei]

ORA-01555 snapshot too old: rollback segment number string with name "string" too small

Cause: Rollback records needed by a reader for consistent read are overwritten by other writers.

Action: If in Automatic Undo Management mode, increase the setting of UNDO_RETENTION. Otherwise, use larger rollback segments.

ORA-02063 preceding stringstring from stringstring

Cause: An Oracle error was received from a remote database link.

Action: Refer to the preceding error message(s).

看下解决方法，应该可以明白点吧