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z/OS V1.11 Communications Server Offers Many Enhancements

z/OS V1.11 Communications Server Offers Many Enhancements - Performance is increased through new functionality

IBM announced z/OS V1.11 Feb. 24, and the new release contains a wide variety of functional extensions; usability and security enhancements; system-management and accountability improvements; and performance, scalability, throughput optimization and expansion features. In fact, z/OS V1.11 continues the long z/OS tradition of release-to-release performance improvement—a rarity in my experience with OS products. How often have you heard another OS claim a new release performs better, with better throughput and resource utilization, than the one it’s replacing? In the other hardware platforms I work with, it’s a rarity if even it even occurs once. Yet, release after release, z/OS not only makes that claim, it proves it in installation after installation.

z/OS Communications Server is one of the major components in V1.11, and performance improvement is central to a wealth of new function and extensive improvements. z/OS Communications Server provides performance enhancements in workload balancing, TCP/IP throughput, z/OS Sysplex Distributor, Queued Direct I/O (QDIO) and other networking aspects. System configuration is simplified, security is tightened, APIs are enhanced, network protocol support is expanded, product packaging is improved and usability is enhanced. Here are some z/OS V1.11 Communications Server highlights:

Responsive Network Performance

z/OS V1.11 provides Enterprise Workload Manager (WLM) interfaces, which allow the Communications Manager to exploit the Sysplex Distributor more efficiently, dispatch network workload in a sysplex via a new connection-routing accelerator and to improve load-balancing determination in a multi-tier z/OS server network. In addition, Sysplex Distributor is planned to compute a composite WLM weight—including performance, capacity and health metrics for multiple tiers, and to apply these factors in a multi-tier, z/OS load-balancing construct.

Name-resolution performance—especially when processing repetitive queries—has been improved through implementation of a sysplex-wide resolver cache. TCP bulk transfers—particularly inbound streaming in high-latency, high-bandwidth networks—should attain higher thoughput via a TCP window-size dynamic-tuning facility.

Another performance enhancement is the movement of TCP/IP sockets’ control blocks to 64-bit common storage, thus alleviating 31-bit extended common system area (ECSA) storage required when many TCP/IP sockets are open. Enterprise Extender performance is enhanced through the implementation of a new adaptive rate-based (ARB) algorithm, reduction in the number of path switches and reduced CPU consumption for IP security (IPSec)—including improved z9 Integrated Information Processor (zIIP)-processor utilization.

The z/OS V1.11 Communications Server will detect and handle a variety of specific sockets programming errors that currently cause extensive performance degradation and availability issues. In addition, a QDIO accelerator function is planned that will operate at the Data Link Control (DLC) level, and will positively impact IP-packet performance when those packets are routed between QDIO and HiperSockets network interfaces. IBM has announced a variety of other performance enhancements.

Jim Schesvold can be reached at

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