IBM z/OS manual Rexx Functions, Communication Services, Dynamic Virtual IP Address Takeover

REXX Functions

z/OS 1.4 extends the REXX language on z/OS when used in a UNIX System Services zSeries REXX environment.

It includes functions for standard REXX I/O and to easily access some common fi le services and environments vari- ables.

Communication Services

z/OS Version 1 Release 6 base elements

z/OS Communications Server (Multiprotocol/HPR Services, TCP/IP Services, SNA/APPN Services)

OSA Support Facility

z/OS Version 1 Release 6 optional no charge features

z/OS Communications Server Security Level 3

The z/OS base includes z/OS Communication Server, which enables: world class TCP/IP and SNA networking support, including enterprise class dependability; performance and scalability; highly secure connectivity; support for multiple protocols; and effi cient use of networking assets.

z/OS can provide near continuous availability for TCP/IP applications and their users with two key features in z/OS: Sysplex Distributor and Dynamic VIPA.

Dynamic Virtual IP Address Takeover

VIPA represents an IP address that is not tied to a specifi c hardware adapter address. The benefi t can be that if an adapter fails, the IP protocol can fi nd an alternate path to the same software, be it the TCP/IP services on a zSeries server or an application.

In case of a failure of the primary IP stack, VIPA Takeover introduced in OS/390 2.8 can support movement to a backup IP stack on a different server in a Parallel Sysplex cluster. Dynamic VIPA Takeover can enhance the initial 2.8 functions, providing VIPA takeback support. This can allow the movement of workload back from the alternate to the primary IP stack.

With Sysplex-Wide Security Associations (SWSA) in z/OS 1.4, IPSec protected workloads are expected to now realize all the benefi ts derived from workload balancing, such as optimal routing of new work to the target system and server application based on QoS and WLM advice, increased availability by routing around failed components and increased fl exibility in adding additional workload in a nondisruptive manner.

Sysplex Distributor

Introduced in OS/390 2.10, Sysplex Distributor is a soft- ware-only means of distributing IP workload across a Parallel Sysplex cluster. Client connections appear to be connected to a single IP address, yet the connections are routed to z/OS images on servers on different zSeries 800/ 900 or S/390 servers. In addition to load balancing, Sys- plex Distributor simplifi es the task of moving applications within a Parallel Sysplex environment.

In z/OS we have taken the functions provided by the Cisco MNLB Workload Agent and Systems Manager, and integrated them into Enhanced Sysplex Distributor. This can eliminate the need for separate Cisco LocalDirector machines in the network and the need for MNLB work- load agents to be run on the zSeries servers. It can also improve performance, while allowing the Sysplex Distribu- tor to decide, based on priority supplied by WLM, the Service Policy Agent and the TCP/IP stack status, on the application instance the packet is sent to.

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