z/TPF support for sub-second retransmission improves TCP/IP performance by reducing the minimum retransmission timeout value for TCP sockets.
Previously, the z/TPF system waited at least 1 second to retransmit a TCP packet. With this APAR, the minimum retransmission timeout value for a TCP packet is reduced to 20 milliseconds. The reduced timeout value is calculated based on the average round trip time and the variance from that average.
PJ43958 takes effect when the APAR is installed. No other action is required.
For more information about z/TPF support for sub-second retransmit see the APEDIT for APAR PJ43958.