IBM Virtual Flash Memory

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The Virtual Flash Memory is designed to improve availability and handling of paging workload spikes when running z/OS V2.1 or higher. The Virtual Flash Memory support with z/OS is designed to help improve system availability and responsiveness using Virtual Flash Memory across transitional workload events, such as market openings and diagnostic data collection.

The Virtual Flash Memory can also be used in coupling facility images to provide extended availability for workloads making use of WebSphere MQ Shared Queues structures. Virtual Flash Memory can help availability by reducing latency from paging delays that can occur at the start of the workday or during transitional periods. Virtual Flash Memory is also designed to help eliminate delays that can occur when collecting diagnostic data during failures.

The initial Virtual Flash Memory represents the amount of Virtual Flash Memory allocated to an activated logical partition. The maximum Virtual Flash Memory amount represents the maximum Virtual Flash Memory the logical partition is allowed. This means, if the initial and maximum amounts are specified, the maximum amount minus the initial amount is the Virtual Flash Memory amount that the logical partition's operating system can dynamically configure.

Notes:
  1. The sum of the maximums for all activated logical partitions cannot exceed 128 TB.
  2. When planning for Virtual Flash Memory, the maximum amount should take into account the Virtual Flash Memory growth required by the partition. If the maximum is reached and the partition wants more Virtual Flash Memory, the change is disruptive for the partition.
The Virtual Flash Memory can be configured in any of the following:
Initial and Maximum specified
The initial amount allocated at activation and amount (initial and maximum) can be configured dynamically
Initial Specified
The initial amount allocated at activation and the logical partition cannot dynamically configure Virtual Flash Memory.
Maximum specified
No initial amount allocated during activation and maximum amount can be configured dynamically when required.
Initial and Maximum not specified
No Virtual Flash Memory planned for the logical partition.