Changing memory settings

You can view and change the settings of the shared and dedicated memory that is assigned to a partition by using the Hardware Management Console (HMC).

Before you begin

You can change the memory that is allocated to the partition. The views and controls that are presented depend on whether the memory is dedicated or shared, an whether the partition is or running or stopped.

Processors use memory to temporarily hold information. Memory requirements for partitions depend on the partition configuration, I/O resources that are assigned, and applications used.

Memory can be assigned in increments of 16 MB, 32 MB, 64 MB, 128 MB, and 256 MB. The default memory block size varies according to the amount of configurable memory in the system. On systems that are managed by an HMC, memory is assigned to partitions using partition profiles.

Dedicated memory is physical system memory that you allocate to a partition that uses dedicated memory 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 partition, the server firmware must have enough memory to complete partition tasks. 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 that are used by the dedicated memory partitions
Maximum memory values allocated to the dedicated memory partitions

Note: Firmware level updates can also change the server firmware memory requirements. Larger memory block sizes can exaggerate the memory requirement change.

When you select the maximum memory values for each dedicated memory partition, consider the following points:

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 failed or is about to fail, the server firmware creates a serviceable event. The server firmware can also unconfigure the failing memory module automatically, depending on the type of failure and the deconfiguration policies that you set up by using the Advanced System Management Interface (ASMI). You can also unconfigure a failing memory module manually by 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 initial program load (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. After the managed system starts the maximum possible number of dedicated memory partitions, the managed system distributes the leftover memory resources among the running dedicated memory partitions, in proportion to the required memory values of the dedicated memory partitions.

Using Huge pages can improve performance in specific environments that require a high degree of parallelism, such as in the DB2® database. You can specify huge-page memory that can be used for the shared-memory buffer pools in the DB2 database. For logically partitioned systems, you can specify the minimum, wanted, and maximum number of huge pages to allocate to a partition when you create the partition or partition profile.

On managed systems that support huge-page memory, you can use the HMC to set the value for the huge-page memory pool. You can also specify values for the number of huge pages to allocate to partitions.

To use huge-page memory, you must ensure that your system has adequate memory resources to dedicate to the huge-page memory pool. The huge-page memory pool is a region of the system memory that is mapped as 16 GB page segments and is managed separately from the base memory of the system.

About this task

To view and change the settings of the memory, complete the following steps:

Procedure

In the navigation pane, click the Resources icon .
Click All Systems. The All Systems page is displayed.
In the work pane, select the partition for which you want to view or change the properties and capabilities and click Actions > View Partition Properties. The Properties page is displayed. You can view and change the properties that are listed under the Properties area.
In the Properties area, click the Memory tab to view the properties of the running logical partition that is using the dedicated or the shared memory.
Select a memory mode that is assigned to the selected partition:
- When the partition is in the running state, and the memory is set to the Dedicated mode, complete the following steps:
  1. You can enter a value or adjust the Memory Allocation tab for the assigned memory that is assigned to the partition.
  2. Click Advanced to view the advanced memory settings for the partition.
- When the partition is in the not activated state, and the memory is set to the Dedicated mode, complete the following steps:
  1. You can enter a value or adjust the values for Memory Allocation tab for the maximum, assigned, and minimum memory that is assigned to the partition.
  2. Click Advanced to change the advanced memory settings for the partition.
  3. Select the Enable Active Memory Expansion check box to enable the active memory expansion feature for the partition.
  4. Enter a value for the Active Memory Expansion field. The value must be in the range 1.0 - 10.0.
  5. Select the Huge Page Memory check box to enable the huge-page memory feature for the partition.
  6. Enter values for the Minimum, Assigned, and Maximum fields.
  7. Select the BSR Array check box to allocate barrier-synchronization register (BSR) arrays to the partition.
  8. Enter values for the Total, Assigned, and Available fields.
  9. From the Memory Mode list select shared to set the mode to shared. You can change the memory mode to shared only when there is a share memory pool is available. Also, you can change the memory mode to shared only when the processor is also set to the shared mode.
  Note: BSR is not supported on POWER8® processor-based servers.
- When the partition is in the running state, and the memory is set to the Shared mode, complete the following steps:
  1. You can enter a value or adjust the Memory Allocation tab for the assigned memory that is assigned to the partition.
  2. Click Avanced to change the advanced memory settings for the partition.
  3. From the Assigned I/O Entitled Memory option, select Auto or Manual.
  4. Enter values for the Assigned I/O Entitled Memory and Memory Weight fields.
- When the partition is in the not activated state, and the memory is set to the Shared mode, complete the following steps:
  1. Change the mode of the memory to shared or dedicated.
  2. Enter a value, or adjust the Memory Allocation tab for the maximum, assigned, and minimum dedicated memory that is assigned to the partition.
  3. Click Avanced to change the advanced memory settings for the partition.
  4. From the Assigned I/O Entitled Memory option, select Auto or Manual. When you select the manual option, you must also enter values for the Assigned I/O Entitled Memory and Memory Weight fields.
  5. From the Memory Mode list select dedicated to set the mode to dedicated.
Optional: Enter a timeout value in the Timeout field.
Optional: Click the Force option to force a particular operation to be performed on the logical partition immediately.
Click Save to apply the changes. Alternatively, click Cancel to reject the changes and close the page.