Improving SNA/CCS Performance

Because SNA/CCS is implemented using a service virtual machine, you can improve the performance of the SNA/CCS environment by allocating more real processor resources to the VSMs that control the terminals connected to CP. Use the CP SET SRM command or the SHARE directory statement to do this. This performance consideration is not specific to SNA/CCS VSMs but applies to all service virtual machines. For more information on the CP SET SRM command, see the z/VM®: CP Commands and Utilities Reference. For more information on the SHARE statement, see SHARE Directory Statement. For more information on performance and the use of the CP SET SRM command and the SHARE statement, see the z/VM: Performance book.

Some installations may see a performance benefit by using the IPOLL function with GCS to poll for pending replies and messages. By allowing GCS to retrieve up to 102 interrupts on each IPOLL, a significant reduction in the number of interrupts to VSCS when it is flooded with incoming IUCVs can be expected. The benefit is greatest when the VSCS virtual machine is loaded with work. The GCS command SET IPOLL ON enables this function.