Performance can vary depending on the number of sessions that the Export driver is using. Using too few sessions can limit the data throughput; using too many sessions involves increased session management overhead which can slow down the job. The latter can occur when running against a large database configuration as the Export driver’s default setting is to have one session per AMP.
There is no general method to determine the optimal number of sessions to use since there are several factors to consider such as the database performance and workload, the network performance, and the volume of data being processed. In many cases, using two or four sessions will result in the best performance, but users are encouraged to experiment with several different session configurations to determine the best setting for each database configuration.