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## 3.7.4 Logical partition storage granularity 

Granularity of main storage for an LPAR depends on the largest main storage amount that is defined for initial or reserved main storage, as listed in Table 3-7. 

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LPAR storage granularity information is required for LPAR image setup and for z/OS RSU definition. LPARs are limited to a maximum size of 16 TB of main storage. However, the maximum amount of memory that is supported by z/OS V2.3 at the time of this writing is 4 TB. 

## 3.7.5 LPAR dynamic storage reconfiguration 

For z/VM V6R3, the limit is 1 TB; for z/VM V6R4 and V7R1, the limit is 2 TB. 

Dynamic storage reconfiguration on z14 servers allows an operating system that is running on an LPAR to add (nondisruptively) its reserved storage amount to its configuration. This process can occur only if unused storage exists. This unused storage can be obtained when another LPAR releases storage, or when a concurrent memory upgrade occurs. 

With dynamic storage reconfiguration, the unused storage does not have to be continuous. 

When an operating system running on an LPAR assigns a storage increment to its configuration, PR/SM determines whether any free storage increments are available. PR/SM then dynamically brings the storage online. 

PR/SM dynamically takes offline a storage increment and makes it available to other partitions when an operating system running on an LPAR releases a storage increment. 

## 3.8 Intelligent Resource Director 

Intelligent Resource Director (IRD) is a z14 and IBM Z capability that is used only by z/OS. 

IRD is a function that optimizes processor and channel resource utilization across LPARs within a single IBM Z server. 

This feature extends the concept of goal-oriented resource management. It does so by grouping system images that are on the same z14 or Z servers that are running in LPAR mode, and in the same Parallel Sysplex, into an  LPAR cluster. This configuration allows WLM to manage resources (processor and I/O) across the entire cluster of system images and not only in one single image. 

