VTAM® performs I/O operations across a channel-to-channel link. By analyzing statistics provided by VTAM, you can select I/O buffer sizes, data transfer delay, and other options that can improve performance of these I/O operations.

VTAM uses channel programs to send data to other hosts. The amount of data that VTAM can read in one operation depends on the number of buffers used by a read channel program and on the size of each buffer.

Each tuning statistics record contains information about the state of data-transfer operations between two VTAMs (using channel-to-channel adapters). Each record contains statistics that cover the time period since the last tuning statistics record was written for that controller or channel-to-channel connection.