System Characteristics that Affect Sessions versus Instances
When specifying the number of sessions and instances to meet the goal of best overall
job performance, consider these other factors:
Number of nodes
Larger Teradata Database systems provide more AMPs, and by default make available
more sessions.
Number and speed of CPUs
The greater the available processing power, the less need there may be for a large
number of parallel sessions. A few connections (sessions) to a very powerful system
can handle the same amount of throughput as a larger number of connections to a less
powerful system.
An imbalance between the throughput capability of the source and target system may
reduce the benefits of using parallel sessions. The operator that interfaces with
the more powerful system may spend excessive time waiting for the operator that interfaces
with the less powerful system to complete its tasks.
Workload
Always attempt to run a Teradata PT job at times when the workload leaves enough available
AMPs for the optimal number of sessions.
I/O bandwidth
Structure of the source or target tables/records
Volume of data being loaded