The log file switch - checkpoint incomplete event tells you that Oracle wants to reuse a redo log file, but the current checkpoint position is still in that log file. This results in redo generation being stopped until the log switch is done. Obviously not good!
To resolve these incomplete checkpoints you need to give the checkpoint process more time to cycle through the logs by doing one or both of the following:
* increase the size of the redo logs
* add more redo log groups
Additionally, consider turning off logging for the temporary tables with transient data using the the NOLOGGING attribute on the tables.
Per Oracle documentation "The NOLOGGING clause specifies that subsequent DML statements (UPDATE, DELETE, and conventional path insert) are unaffected by the NOLOGGING attribute of the table and generate redo." Therefore the SQL Hint /*+ APPEND */ should be used in your application code (only for non-critical, temporary tables).