Primary partitions need a minimum of 256 MB of memory.
The minimum memory of V5R1 and V5R2 secondary partitions is 128 MB. V4R4 and V4R5 secondary partitions minimum memory requirement remains 64 MB. Depending on the number of secondary partitions on the server, the primary partition may need more memory to successfully manage the partitions on the server.
To dynamically move memory, you have to establish a minimum and maximum range within which you can move the resource without needing to restart the logical partition. Changing the maximum value requires a system restart. Changing the minimum value only requires you to restart the partition. Due to performance reasons, you are recommended to specify the maximum value that is close to the amount of memory the partition will use on a regular basis. By specifying a maximum value higher than what is needed for the partition, you waste valuable memory resources. Minimum values dictate what is required to restart the partition. If the minimum value is not met for all logical partitions, only the primary will restart. You can specify a memory minimum value as low as 0. A value of 0 in any partition creates a non-functioning partition. If the primary partition has been restarted (a system restart) after the secondary partition was set to 0, then another system restart is required when the secondary memory value is changed. If the changes are made to the memory within the same primary restart, then a system restart is not required to make changes to the memory allocations.
The full amount of memory that you assign to a logical partition may not be available for the partition's 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.
When you dynamically remove memory from a logical partition, the currently allocated amount may not be reduced to the new value you have specified until you restart the partition. This is dependent upon factors in the running operating system in that partition. Runtime values are based on memory the partition needs to complete an assigned task.