ORA-01555 reports that Oracle is unable to maintain a read consistent view of the table being copied.
For the duration of any single transaction (including 'create table as select') Oracle has to maintain a read consistent image of the tables in the transaction. This is achieved using the original table and where necessary, the rollback segments. Once a transaction has completed, Oracle does not guarantee that it's rollback will be kept in the rollback segment. If this rollback is needed for the consistent image of the table that Space Manager is copying, and it has been lost, then ORA-01555 is returned.
ORA-01555 is returned when Oracle has failed to maintain read consistency. It is a design consideration of Oracle Server, and does not show any product issues with Space Manager.
The issue is that the database rollback segments are being reused before the table copy completes. The ways this can be avoided are;
1. Reduce the need to go back to the rollback segment by running the reorg when the data in the table is changing less quickly.
2. Increase the size of the rollback segment so that Oracle can maintain the read consistent image for longer.
3. Tune the reorg so that the read consistent image does not need to be kept for so long.
The data in the table will be changing less often when the system is quieter. Your DBA can re-size your rollback segments, note Oracle recommend all rollback segments are the same size. Parallel options in Space Manager will allow you to tune the reorg and this may result in a shorter elapsed time for the table copy.
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