IBM Power7 Optimization And Tuning Manual page 98

For more information about this topic, see 4.4, "Related publications" on page 94.
Workload partitions (WPAR shared LPP installs)
Starting with AIX V6.1, the WPAR feature gives the system administrator the ability to easily
create an isolated AIX operating system that can run services and applications. WPAR
provides a secure and isolated environment for enterprise applications in terms of process,
signal, and file system space. Any software that is running within the context of a workload
partition appears to have its own separate instance of AIX.
The usage of multiple virtual operating systems within a single global operating environment
can have multiple advantages. It increases administrative efficiency by reducing the number
of AIX instances that must be maintained.
Applications can be installed in a shared environment or a non-shared environment. When an
application is installed in a shared environment, it means that it is installed in the global
environment and then the application is shared with one or more WPARs. When an
application is installed in a non-shared environment, it means that it is installed in the WPAR
only. Other WPARs do not have access to that application.
Shared WPAR installation
A shared installation is straightforward because installing software in the global environment
is accomplished in the normal manner. What must be considered is whether the system
WPARs that share a single installation will or will not interfere with each other's operation.
For software to function correctly in a shared-installation environment, the software package
must be split into shareable and non-shareable files:
Shareable files (such as executable code and message catalogs) must be installed into
the shared global file systems that are read-only to all system WPARs.
Non-shareable files (such as configuration and runtime-modifiable files) must be installed
into the file systems that are writable to individual WPARs. This configuration allows
multiple WPARs to share a single installation, yet still have unique configuration and
runtime data.
In addition to splitting the software package, the software installation process must include a
synchronization step to install non-shareable files into system WPARs. To accomplish this
task, the application must provide a means to encapsulate the non-shareable files within the
shared global file systems so that the non-shared files can be extracted into the WPAR by
some means. For example, if a vendor creates a custom-installation system that delivers files
into /usr and /, then the files that are delivered into / must be archived within /usr and then
extracted into / using some vendor-provided mechanism. This action can occur automatically
the first time that the application is started or configured.
Finally, the software update process must work so that the shareable and non-shareable files
stay synchronized. If the shared files in the global AIX instance are updated to a certain fix
level, then the non-shared files in individual WPARs also must be updated to the same level.
Either the update process discovers all the system WPARs that must be updated or, at start
time, the application detects the out-of-synchronization condition and applies the update.
Some software products manage to never change their non-shaerable files in their update
process, so they do not need any special handling for updates.
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