VTAM® performs I/O operations to channel-attached communication controllers and cluster controllers.

You can use VTAM tuning statistics to adjust operands in NCP and VTAM definition statements to make your system run more efficiently.

VTAM uses channel programs to send data to SNA controllers. 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 VTAM and one channel-attached SNA controller (communication or cluster controller). 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.