IP Services: Verify the new default for the QUEUEDRTT parameter
Description
In z/OS V2R2, enhancements were made to the Communications Server outbound serialization function, which is controlled by the QUEUEDRTT parameter on the TCPCONFIG profile statement. The default value for this parameter is changed. Previously, the default setting for QUEUEDRTT was 20, meaning that only TCP/IP connections with a round-trip time (RTT) value of 20 milliseconds or more are eligible to use outbound serialization. In z/OS V2R2, the default value for QUEUEDRTT is changed to 0, meaning that all TCP/IP connections are eligible to use outbound serialization.
Table 1 provides more details about this migration action. Use this information to plan your changes to the system.
| Element or feature: | z/OS Communications Server. |
|---|---|
| When change was introduced: | z/OS V2R2. |
| Applies to migration from: | z/OS V2R1 and z/OS V1R13. |
| Timing: | Before the first IPL of z/OS V2R2. |
| Is the migration action required? | Yes, if you do not specify the QUEUEDRTT parameter on the TCPCONFIG profile statement. |
| Target system hardware requirements: | None. |
| Target system software requirements: | None. |
| Other system (coexistence or fallback) requirements: | None. |
| Restrictions: | None. |
| System impacts: | The new default value allows more connections to be eligible for outbound serialization. This performance optimization might result in higher CPU costs at the sending host, but these costs are offset by the CPU savings on the receiving host. |
| Related IBM® Health Checker for z/OS® check: | None. |
Steps to take
If you do not currently specify the QUEUEDRTT parameter on the TCPCONFIG profile statement, but you want to continue using a value of 20 milliseconds as the threshold to enable a TCP/IP connection to use outbound serialization, you must specify QUEUEDRTT 20 on the TCPCONFIG profile statement.
Reference information
- See the QUEUEDRTT parameter description in TCPCONFIG statement in z/OS Communications Server: IP Configuration Reference.
- See Outbound Serialization in z/OS Communications Server: IP Configuration Guide.