This topic provides information about i5/OS® memory requirements for i5/OS logical partitions.
Before you use this information, you should familiarize yourself with general memory concepts in a logical partitioning environment.
Dynamic memory changes on i5/OS logical partitions affect the base memory pool of the logical partitions (*BASE pool). Private memory pools or shared memory pools are not affected. Dynamic memory changes cannot cause the amount of memory in the base pool to fall below the minimum amount of memory required in the base pool (as determined by the base storage minimum size (QBASPOOL) system value). If a dynamic memory change would cause the base pool to fall below this amount, the system releases excess memory pages only after keeping the minimum amount of memory required in the base pool.
To prevent any data loss during dynamic memory movement, the system first writes any data from memory pages to the disks before making the memory pages available to another partition. Depending on the amount of memory you have requested to move, this might take some time.
The full amount of memory that you assign to a logical partition might not be available for the logical partition to use. Static memory overhead required to support the assigned maximum memory will affect the reserved or hidden memory amount. This static memory overhead will also influence the minimum memory size of a partition.
If you change the minimum memory amount of a logical partition, then you must restart the logical partition for the change to take effect. If you change the maximum memory amount of a logical partition, then you must restart the logical partition for the change to take effect, and you might also need to restart the managed system or change the minimum memory amount.