3.7.4 Logical partition storage granularity 3.7.5 LPAR dynamic storage reconfiguration 3.8 Intelligent Resource Director 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.  Table 3-7 Logical partition main storage granularity (z14) 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.  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. 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. Chapter 3. Central processor complex system design  135 Logical partition:  Largest main storage amount  Logical partition:  Main storage granularity  Main storage amount </= 512 GB 1 GB 512 GB < main storage amount </= 1 TB 2 GB 1 TB < main storage amount </= 2 TB 4 GB 2 TB < main storage amount </= 4 TB 8 GB 4 TB < main storage amount </= 8 TB 16 GB 8 TB < main storage amount </= 16 TB 32 GB