If your rollback segments are not configured correctly, very large or complex database queries can, under certain conditions, result in an Oracle error:
ORA-01555 "snapshot too old (rollback segment too small)"
This occurs when rollback information is overwritten so that Oracle cannot roll back committed database changes to attain a sufficiently old enough version of the database block. For example, this could affect large jobs run using the CA DataMinder Event Import or Data Indexer utilities.
To prevent this error, you may need to increase the size of your existing rollback segments and create additional rollback segments. These steps allow pending database changes to be spread across more segments and reduce the risk of overwriting required rollback information. Although the exact size varies for each CA DataMinder installation, very large installations typically need rollback segments of 30Gb.
For guidelines about managing your rollback segments, see the relevant chapter in the Oracle Administrators Guide.
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