Application programming interface (API) performance considerations

To achieve better performance with your iSeries™ server, you need to consider the application programming interface (API) available on the iSeries server. To optimize APPC performance, consider the following:

• Using larger sends (record sizes) for a large transfer provides a higher application data rate and decreases CPU time. With the larger record size, the CPU has less processing to do because there are fewer application reads and writes to transfer the same amount of data.
• If a value of *CALC is selected for maximum Systems Network Architecture (SNA) request/response unit (RU), the system selects an efficient size compatible with the frame size. The frame size is on the line description that you choose. Changing the RU size to a value other than *CALC may negate this performance feature.
• Compression with APPC should be used with caution and only for slower speed wide area network (WAN) environments. Many suggest that compression should be used with speeds 19.2 kbps and slower.
• If you are doing tasks that include repetitive, small puts; better performance is achieved if you use ICF or CPI Communications.

See the following topics for a more complete discussion of APPC applications:

• Performance considerations for Intersystem Communications Function
• Performance considerations for Common Programming Interface communications

For information about iSeries server communications, see the Communications Configuration book.

For more information about CICS/400®, see the CICS® for iSeries Administration and Operations Guide .