Active Memory Expansion for AIX logical partitions

When you enable Active Memory Expansion for an AIX® logical partition, you increase the memory capacity of the logical partition without assigning more memory to it. The operating system compresses a portion of the memory that the logical partition uses. This compression creates space for more data and expanding the memory capacity of the logical partition.

When you expand the memory capacity of a logical partition, you enable the logical partition to do more work with the same amount of memory. This can be especially useful when you want to increase the workload of a logical partition, but cannot assign more memory to the logical partition. When you expand the memory capacity of several logical partitions on a server, you increase the overall memory capacity of the server. This can be especially useful when you want to consolidate more workloads onto the server by creating more logical partitions.

You can configure the degree of memory expansion that you want to achieve for a logical partition by setting the Active Memory Expansion factor in a partition profile of the logical partition. The expansion factor is a multiplier of the amount of memory that is assigned to the logical partition. For example, if the amount of memory that is assigned to a logical partition is 25 GB and the expansion factor is set to 2.0, then the desired memory capacity of the logical partition is 50 GB. In this situation, the operating system attempts to compress data such that 50 GB of data fits into 25 GB of memory. After you set the expansion factor, you can monitor the performance of the logical partition and then dynamically change the expansion factor to improve performance.

When you configure a logical partition to use Active Memory Expansion, you must also configure some additional processing resources for the logical partition. The operating system uses the additional processing resources to perform the memory compression. The amount of processing resources that the logical partition requires depends on the workload that is running in the logical partition and the expansion factor that you set for the logical partition.

You can configure Active Memory Expansion for logical partitions that use dedicated memory and logical partitions that use shared memory.