LPAR:

In computing, a logical partition, commonly called an LPAR, is a subset of computer's hardware resources, virtualized as a separate computer. In effect, a physical machine can be partitioned into multiple LPARs, each housing a separate operating system.
The technology was initially developed by IBM for mainframe architecture ESA/390 around 1990, and continued also for zSeries and System z9 architectures. However, IBM later extended the idea to non-mainframe servers, such as pSeries and iSeries, albeit with varying technical specifications. Multiple operating systems are compatible with LPARs, including z/OS, z/VM, z/VSE, z/TPF, AIX, Linux (including Linux on zSeries), and i5/OS.

Through advanced dynamic logical partitioning (LPAR) capabilities, a single partition can act as a completely separate i5/OS, Linux or AIX server. System i platforms can automatically adjust pooled processor resources across multiple operating systems, borrowing processing power from idle partitions to handle high transaction volumes in other partitions.

With LPAR on the System i platform, you have both the power and flexibility to address multiple system requirements in a single machine. LPAR supports up to 10 dynamic logical partitions per processor. So, depending upon the System i model, you can run up to 254 independent servers—each with its own processors and memory resources within a single physical System i system.

Consolidating systems with LPAR can help cut operational costs, improve availability, ease management and improve service levels, while allowing businesses to quickly deploy applications. LPAR technology can even enhance your ability to simplify networks and centralize multiple business operations.