SA-4395

Summary

The administrator is observing the following error while running a long BIX export: -

Error Messages

2014-11-27 19:11:12,768 [ main] [ ] ( internal.access.ExtractImpl) ERROR - Snapshot too old error occured while getting source rows
2014-11-27 19:11:12,768 [ main] [ ] ( internal.access.ExtractImpl) ERROR - Consider increasing rollback segments or extracting less data in a run
2014-11-27 19:11:12,810 [ main] [ ] ( internal.access.ExtractImpl) INFO - Elapsed Time (seconds): 2939.749
2014-11-27 19:11:12,810 [ main] [ ] ( internal.access.ExtractImpl) INFO - Total CPU Time (seconds): 0.0
2014-11-27 19:11:12,810 [ main] [ ] ( internal.access.ExtractImpl) INFO - #Instances Extracted: 0
2014-11-27 19:11:12,810 [ main] [ ] ( internal.access.ExtractImpl) INFO - #Instances per second: 0.0
2014-11-27 19:11:12,810 [ main] [ ] ( internal.access.ExtractImpl) INFO - #Instances per hour: 0.0
2014-11-27 19:11:12,810 [ main] [ ] ( internal.access.ExtractImpl) INFO - #Instances not extracted due to errors: 0

Root Cause

The error is not related to BIX trying to update the database but rather to the Oracle read consistency mechanism.
If some of the data has changed between the time that the query was first initiated until the time that it has completed, then Oracle will still present the data at the time that the query was initiated. And will retain any delta changes in the rollback segment.

However,if this is a large query and the rollback segment isn't sufficiently sized to deal the number of changes within that results set, then this will generate an ORA-01555 error, and will be accompanied by BIX showing the above error in the logs.

Resolution

Two solutions are as follows:
1. Have the DBA increase the rollback segment size such that the BIX run can complete before the rollback segment is full
2. Run more frequent BIX runs so that we don't take long to extract data hence reducing the chances of running into a ORA-01555