## 3.6.4 Virtual Flash Memory 

IBM Virtual Flash Memory (VFM) is the replacement for the Flash Express features that were available on the IBM zEC12, zBC12, IBM z13fi , and IBM z13s. No application changes are required to change from IBM Flash Express to VFM. 

On z14 ZR1, up to four Virtual Flash Memory features (FC 0614) can be ordered. One VFM feature has 512 GB on z14 ZR1. 

## 3.7 Logical partitioning 

## 3.7.1 Overview 

The logical partitioning features are described in this section. 

Logical partitioning is a function that is implemented by the PR/SM$^{6}$. z14 ZR1 can be managed in standard or Dynamic Partition Manager (DPM) modes. DPM provides a dynamic LPAR and resource management of the z14 ZR1 and uses a graphical, interactive interface to the PR/SM. 

## HiperDispatch 

PR/SM and z/OS work in tandem to use processor resources more efficiently. HiperDispatch is a function that combines the dispatcher actions and the knowledge that PR/SM has about the topology of the system. 

Performance can be optimized by redispatching units of work to the same processor group, which keeps processes running near their cached instructions and data, and minimizes transfers of data ownership among processors in different PU SCMs. 

The nested topology is returned to z/OS by the Store System Information (STSI) instruction. HiperDispatch uses the information to concentrate logical processors around shared caches (L3 at PU chip level, and L4 at drawer level), and dynamically optimizes the assignment of logical processors and units of work. 

z/OS dispatcher manages multiple queues, called affinity queues , with a target number of eight processors per queue, which fits well onto a single PU chip. These queues are used to assign work to as few logical processors as are needed for an LPAR workload. Therefore, even if the LPAR is defined with many logical processors, HiperDispatch optimizes this number of processors to be near the required capacity. 

Tip:  z/VM V6.3 and later also support HiperDispatch, which is required for activating SMT. (z14 ZR1 supports z/VM V6.4 or newer.) 

## Logical partitions 

PR/SM enables z14 ZR1 servers to be started for a logically partitioned operation, supporting up to 40 LPARs. Each LPAR can run its own operating system image in any image mode, independently from the other LPARs. 

