new vendor package that runs under AIX. As guests of VM/ESA, all three can
run efficiently while sharing one processor.
•
You have production applications that need to be reworked to comply with
Year 2000. With VM/ESA′s Guest Support you can bring up a duplicate of
your production system, set the clock to a date and time beyond the year
2000 then perform test and application debugging without disrupting your
current production system.
•
You have production applications that need to be reworked to comply with
changes required by the European Common Currency. With VM/ESA′s Guest
Support you can bring up a duplicate of your production system, set the
specific elements that affect currency and/or exchange rates, then perform
test and application debugging without disrupting your current production
system.
•
If you are considering using Parallel Sysplex. VM/ESA supports guest
coupling simulation on the IBM 9672 Parallel Enterprise Servers Generation 3
and Generation 4 and on the IBM Multiprise 2000 Servers (at the appropriate
engineering change levels). VM/ESA Guest Coupling Simulation provides for
the simulation of one or more complete parallel sysplexes within a single
VM/ESA system image. The intent is to provide a pre-production testing
platform for a coupled-system installation. Other than the processors
required, there is no special hardware needed: no coupling links and no
external coupling facilities. All guest operating systems coupled within a
simulated sysplex can only be coupled (through simulated coupling links) to
coupling facilities also running as guests of the same VM/ESA system. Up to
32 virtual machines can be coupled within a simulated sysplex, with each
such virtual machine coupled to up to eight coupling facility virtual machines.
Performance Benefits
Guest systems may see performance improvements by exploiting VM/ESA
features. For example, both virtual disk in storage and minidisk cache allow
guests to avoid real I/Os by using data in storage and caching techniques.
Reduced Hardware and Migration Cost
Guest systems such as OS/390, MVS, TPF, VSE, VM and others can share
devices such as channels, printers, and DASD, which VM/ESA efficiently
manages. VM/ESA adds value to such devices merely by the way it manages
them. A good example is VM/ESA′s minidisk support, which allows one real disk
to function as if it were several smaller disks (such as multiple IPL-able
minidisks). VM/ESA also simulates some hardware devices (such as unit record
devices and CTC adapters).
For migrating to a new release from an older VM, VSE, MVS, OS/390, or TPF,
VM/ESA gives you the ability to bring up the new system on the same physical
processor saving you the cost of a separate processor or LPAR hardware. This
new system can share the devices and resources of your existing VM/ESA
system thus eliminating the cost of separate hardware for new system migration
testing. When testing is complete switching over to your new production system
is only a matter of configuration/table changes and can be accomplished in
minutes. These technical and cost saving advantages provided by VM/ESA and
VM′s Guest Support are fundamental requirements upon which the VM/ESA
product was built and have been carefully refined over the years. This gives
Chapter 26. Test Environments 427
