Logical Partitioning (LPAR)

Technote (troubleshooting)


Problem(Abstract)

This document provides answers to frequently asked questions about logical partitioning.

Resolving the problem

Q: What is LPAR?

A: LPAR is an acronym for Logical Partitioning. Logical partitioning is the allocation of system resources in such a way to create systems that are contained in the same physical footprint, but are logically separated from each other.

System resources include:

o Processors
o Main Storage (for example, memory)
o Interactive Performance
o System buses
o IOPs and their attached devices
Each partition operates as a complete system.

Each partition has its own:
o Address space
o Auxiliary Storage Pools (ASPs)
o Memory Pools
o Processors
o Problem Logs, LIC Logs, PAL entries, and so on
o Data (libraries, objects, file systems, and so on
o Performance characteristics
o Language feature code(s)
o SLIC, IBM® OS/400®, and LPPs
Software errors are isolated in each partition.

Q: What are the base requirements for LPAR?
A: For the 6xx, 7xx, and Sxx models, LPAR requires at a minimum an N-way (2, 4, 8, or 12-way) system. The 8xx models support LPAR and can take advantage of shared processors with V5R1. The model 150 and model 170 do not support LPAR. Certain model 270 systems support Logical Partitioning and shared processors.

A list of model 8xx and 270 servers that support LPAR can be located at the following Web site:

http://www-1.ibm.com/servers/eserver/iseries/lpar/chart.htm

Q: Which releases support LPAR?
A: V4R4 is the first and earliest release which supports LPAR. V4R5 and later releases also support Logical Partitioning.

Q: Why would I want to partition my IBM® AS/400® / IBM® iSeries™ system?
A: Potential scenarios why someone might want to create logical partitions on their AS/400 / iSeries system include:
Consolidation Combine several AS/400 / iSeries servers to a larger AS/400 / iSeries system. Each server operates in a separate logical partition which maintains the software isolation of those systems. The total cost for the environment is reduced.
Release Migration Test a new release of OS/400, vendor application, or other product on a partition before rolling the new release to the production partition.
Mixed Production, Test Environments,
and Departmental Systems
A partitioned system can be shared by multiple projects or departments, simplifying cost justification and cost accounting requirements. Partitions allow test/development work to continue without adversely affecting production work.
Constrained Systems Workloads that cannot fully use a large system (because of contention for example), may perform better when the workload is run as multiple images using partitions.
Diverse Workloads Workloads that may not run well together on a single system can be isolated from each other via partitions. For example, a general purpose interactive and batch workload comprised of payroll, forecasting and planning and another workload for inventory control.
Q: What is the difference between the primary partition and a secondary partition?
A: The primary partition provides some general functions on which all partitions are dependent. It is the only partition active on a single partition system. It always exists and is defined. Partition management functions are performed from the primary partition. A secondary partition is any partition which is not the primary partition. Secondary partitions operate independently of other secondary partitions. Keep in mind that if the primary partition fails then all partitions will fail. Powering off the primary partition powers off the entire physical system.

Q: Can my partitions be at different releases?
A: Yes. The general rule is that the range of supported releases is ±1 from the release of the primary partition. As with any rule, there are exceptions:
1 V4R3 cannot run in a partition on any model.
2 V4R4 cannot run in a partition on a model 8xx system.
3 For a 6xx or 7xx system with V4R4 running in the primary partition, V5R1 is allowed in a secondary partition.
4 Certain 8xx models will only allow V4R5 to run in a secondary partition.
5 Certain 8xx models require V5R2.
6 Certain hardware models allow a secondary partition release that is +2 from the primary partition.
Additional release information can be found at:

http://publib.boulder.ibm.com/infocenter/systems/scope/i5os/index.jsp?topic=/rzait/rzaitreleasesupport.htm

Q: Where can I find more information about LPAR?
A: Additional LPAR information, including links to LPAR documentation, can be located at the following URLs:

To access the Information Center, go to the following Web site:

http://publib.boulder.ibm.com/iseries/

To access the iSeries Technology Center (iTC), go to the following Web site:

http://www-1.ibm.com/servers/eserver/iseries/lpar/

Historical Number

16035902

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Document information


More support for:

IBM i
Internals

Software version:

5.3.0, 5.3.5, 5.4.0, 5.4.5, 6.1.0

Operating system(s):

IBM i

Reference #:

N1018053

Modified date:

2012-08-26

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