We see this error on a number of tables when doing an expdp on 12c / Windows.
A restart of the Oracle database service makes this go away...
Can anyone shed some light on what may cause this and the best way to manage it.
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[oracle@orcluat ~]$ oerr ora 01555 01555, 00000, "snapshot too old: rollback segment number %s with name \"%s\" 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 undo_retention // setting. Otherwise, use larger rollback segments
During data pump export, it's session reads rows from tables being exported and rows are consistent to the point in time when the
expdp session has started reading the table. If you want all tables in the export to be consistent to the same point in time, you need to use the
If the rows of the table being read are changed then server process has to make the rows consistent by using undo information. But it is unable to obtain the required undo, which might have been replaced by new undo information(controlled by undo_retention,there are certain condition where undo retentation may be ignored, initialization parameter).
As we don't know what exactly had happened in your case, we can only give some generic solutions.
oerrutility, increase the value of
undo_retention, presumably you are using automatic undo management. Make sure you have enough space on undo tablespace to satisfy the retention time.