Performance considerations for intersystem communications function

You can use intersystem communications function (ICF) to write application programs that you want to communicate with advanced program-to-program communications (APPC). ICF also provides program-to-device communications between the iSeries™ system and hardware devices. You must determine which system is to send data first before you write the program. ICF data management handles the communication functions and the data for your program. In particular, ICF should be used to do tasks that include repetitive, small inputs.

To optimize ICF performance, consider the following:

• Eliminate unused record formats.
• Use separate record formats instead of multipurpose record formats with option indicators.
• Code to use the same record format for repeated operations.
• Set the maximum program devices equal to 1.
• Use a nonshared file.
• Use a separate indicator area.
• The use of the ICF keywords force data and confirm should be minimized.
• Use the Request to Send keyword only when necessary.
• Use the Invite Only keyword when soliciting input from multiple devices, otherwise use the Read keyword instead.
• If using the Invite keyword to solicit from multiple program devices, follow it with a Read-from-invited operation, not a Read operation.

To create device descriptions to get your system set up for ICF, do the following:

1. Type the appropriate Create Device Description commands on the iSeries system command line and press F4.
2. Use the online help information to choose the parameter values.
3. Press Enter. The device description is created.

For more information about ICF, see

• Application programming interface (API) performance considerations
• ICF Programming