Dedicated memory

Dedicated memory is physical system memory that you assign to a logical partition that uses dedicated memory (hereafter referred to as a dedicated memory partition), and is reserved for use by the dedicated memory partition until you remove the memory from the dedicated memory partition or delete the dedicated memory partition.

Depending on the overall memory in your system and the maximum memory values you choose for each logical partition, the server firmware must have enough memory to perform logical partition tasks. The amount of memory required by the server firmware varies according to several factors. The following factors influence server firmware memory requirements:

• Number of dedicated memory partitions
• Partition environments of the dedicated memory partitions
• Number of physical and virtual I/O devices used by the dedicated memory partitions
• Maximum memory values given to the dedicated memory partitions

When selecting the maximum memory values for each dedicated memory partition, consider the following:

• Maximum values affect the hardware page table (HPT) size for each dedicated memory partition
• The logical memory map size for each dedicated memory partition

If the server firmware detects that a memory module has failed or is about to fail, the server firmware creates a serviceable event. The server firmware can also deconfigure the failing memory module automatically, depending on the type of failure and the deconfiguration policies that you set up using the Advanced System Management Interface (ASMI). You can also deconfigure a failing memory module manually using the ASMI. If a memory module failure causes the entire managed system to shut down, the managed system restarts automatically if the managed system is in normal IPL mode. When the managed system restarts itself, or when you restart the managed system manually, the managed system attempts to start the dedicated memory partitions that were running at the time of the memory module failure with their minimum memory values. If the managed system does not have enough memory to start all of the dedicated memory partitions with their minimum memory values, the managed system starts as many dedicated memory partitions as it can with their minimum memory values. If any memory is left over after the managed system has started as many dedicated memory partitions as it can, the managed system distributes the remaining memory resources to the running dedicated memory partitions in proportion to their desired memory values.