SMF Type 50 Record

The SMF 50 format depends upon the resource for which the tuning I/O operation is collected. The following format is used for the tuning statistics for input/output (I/O) operations for SNA controllers

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.

The SMF 50 format depends upon the resource for which the tuning I/O operation is collected. The following format is used for the tuning statistics for I/O operations for channel-to-channel connections.

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

The SMF 50 format depends upon the resource for which the tuning I/O operation is collected. The following format is used for for I/O operations for multipath channel (MPC) connections using XCF. (Multipath channel (MPC) connections use XCF or channel connectivity.)

With XCF multipath channel attachment, VTAM uses the MVS XCF signaling facility to send data to other hosts. By analyzing statistics provided by VTAM, you can select I/O buffer sizes and other options that can improve performance of these I/O operations. The amount of data that VTAM can read in one operation depends on the size of the read buffer.

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

Notes: 1. Indicates fields used only in the first record for statistics on the group.
2. Indicates fields used only in the subsequent record for statistics on the read/write subchannel.
3. TSWEEP and QSWEEP are always 0 for HPDT MPC connections.

The SMF 50 format depends upon the resource for which the tuning I/O operation is collected. The following format is used for I/O operations for multipath channel connections using channels. (Multipath channel (MPC) connections use XCF or channel connectivity.)

With MPC channel connectivity attachment, VTAM performs I/O operations across multiple single-direction channel links. 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 or Direct Memory Access (DMA) to transmit and receive data. The amount of data that VTAM can read in one operation depends on the size of the read buffer. Each tuning statistics record contains information about the state of data-transfer operations across the multipath channel connection.

Each record contains statistics that cover the time period since the last tuning statistics record was written for that multipath channel connection.

Note: Non-HPDT multipath channel uses a special data block called a sweep that is exchanged with the adjacent host to verify that data has not been lost. A host initiating a sweep request holds all outbound multipath channel transmissions until it receives a sweep reply from the adjacent host.

A sweep is initiated when either of the following occurs:

• A timer expires in the host with the higher subarea number.
• Receive queue depth in either host is excessive.

The host initiating the sweep sends the sequence number of the last output transmit block. The adjacent host compares this number with its last input transmit block sequence number. The adjacent host then sends a response to the initiating host that includes the adjacent host last output transmit block sequence number. The initiating host makes the same comparison. If the numbers do not match, or the sweep does not complete within a time limit, the multipath channel group will be inactivated. Otherwise, normal flow continues. The tuning statistics contain a count of how many sweeps are initiated by an expired timer and how many are initiated by excessive receive queue depth.

Note: For HPDT MPC connections, tsweep and qsweep are always 0.

Notes: 1. Indicates fields used only in the first record for statistics on the group.
2. Indicates fields used only in subsequent records for statistics on each write and each read subchannel.
3. TSWEEP and QSWEEP are always 0 for HPDT MPC connections.
4. Indicates fields used only in subsequent records for statistics on each OSA-Express or Hipersockets datapath queue

The SMF 50 format depends upon the resource for which the tuning I/O operation is collected. The following format is used for Tuning statistics for input/output (I/O) operations for TCP connections.

VTAM performs I/O operations across TCP connections. By analyzing statistics provided by VTAM, you can improve performance of I/O operations.