176 IBM eServer zSeries 900 Technical Guide
5.1 Parallel Sysplex
Figure 5-1 illustrates the components of a Parallel Sysplex as implemented within the zSeries
architecture. Shown is an ICF connected between two z900 servers running in Sysplex, and
there is a second integrated Coupling Facility defined within one of the z900s containing
Figure 5-1 Sysplex hardware overview
Shown also is the connection required between the Coupling Facility defined on a turbo
model (2064-2xx), and the sysplex timer, to support Message Time Ordering. Note that
Message Time Ordering requires a CF connection to the Sysplex Timer whenever:
– The Coupling Facility is an LPAR or ICF on a turbo model (the z900 model 100
Coupling Facility is non-turbo).
– The server does not have sysplex timer connectivity to the Parallel Sysplex supported
by the CF partition.
5.1.1 Parallel Sysplex described
Parallel Sysplex technology is an enabling technology, allowing highly reliable, redundant, and
robust zSeries technologies to achieve near-continuous availability. A Parallel Sysplex is
comprised of one or more z/OS and/or OS/390 operating system images coupled via
Coupling Facility. The images can be combined together to form clusters. A properly
configured Parallel Sysplex cluster is designed to maximize availability. For example:
Hardware and software components provide for concurrent planned maintenance, like
adding additional capacity to a cluster via additional images, without disruption to
DASD DASD DASD
ESCON / FICON
CF on a Turbo
model to Sysplex
Chapter 5. Sysplex functions 177
Networking technologies that deliver functions like VTAM Generic Resources, Multi-Node
Persistent Sessions, Virtual IP Addressing, and Sysplex Distributor to provide
fault-tolerant network connections.
z/OS and OS/390 software components allow new software releases to coexist with lower
levels of that software component to facilitate rolling maintenance.
Business applications are “data sharing enabled” and cloned across images to allow
workload balancing and to prevent loss of application availability in the event of an outage.
Many operational and recovery processes can be automated, reducing the need for
The Parallel Sysplex is a way of managing this multi-system environment, providing the
Dynamic workload balancing
Simplified systems management
Single system image
Within a Parallel Sysplex cluster it is possible to construct a parallel processing environment
with high availability. This environment is composed of one or more images which provide
concurrent access to all critical applications and data.
You can introduce changes (such as software upgrades) one image at a time, while remaining
images continue to process work. This allows you to roll changes through your images at a
pace that makes sense for your business.
The Parallel Sysplex environment can scale, in a nearly linear fashion, from 2 to 32 images.
This can be a mix of any servers or operating systems that support the Parallel Sysplex
environment. The aggregated capacity of this configuration meets every processing
requirement known today.
Dynamic workload balancing
The entire Parallel Sysplex cluster can be viewed as a single logical resource to end users
and business applications. Work can be directed to any like operating system image in a
Parallel Sysplex cluster having available capacity. This avoids the need to partition data or
applications among individual images in the cluster or to replicate databases across multiple
Workload management permits you to run diverse applications across a Parallel Sysplex
cluster while maintaining the response levels critical to your business. You select the service
level agreements required for each workload, and the z/OS or OS/390 Workload Manager
(WLM), along with the subsystems such as CP/SM or Websphere, automatically balances
tasks across all the resources of the Parallel Sysplex cluster to meet your business goals.
Whether the work is coming from batch, SNA, TCP/IP, DRDA, or MQSeries (non-persistent)
messages, dynamic session balancing gets the business requests into the system best able
to process the transaction. This provides the performance and flexibility you need to achieve
the responsiveness your customers demand, and it is invisible to the users.