All page and chapter references in this document refer to:
IBM Redbook - IBM System z9 Enterprise Class Technical Guide - SG24-7124
Maximum physical memory sizes are directly related to the number of books in the system. Each book may contain a maximum of 128 GB of physical memory. Physical memory is organized in two banks of four memory cards each. One bank of four memory cards in each book is always populated. The memory size per bank per book may differ. Also, memory sizes in each book do not have to be similar; different books may contain different amounts of memory. The minimum orderable amount of memory is 16 GB, system-wide.
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A one-book system (z9 EC Model S08) may contain 16 GB, 32 GB, 64 GB, or 128 GB of physical memory. Memory is orderable in 16 GB increments for customer use.
- A two-book system (z9 EC Model S18) may contain up to a maximum of 256 GB of physical memory. For memory card distribution variations in newly built two-book systems, refer to Table 2-2 on page 31. Memory is orderable in 16 GB increments for customer use.
- A three-book system (z9 EC Model S28) may contain up to a maximum of 384 GB of physical memory. For memory card distribution variation in a newly built three-book system, refer to Table 2-2 on page 31. Memory is orderable in 16 GB increments for customer use.
- A four-book system (z9 EC Model S38 or z9 EC S54) may contain up to a maximum of 512 GB of physical memory. For memory card distribution variation in a newly built four-book system, refer to Table 2-2 on page 31. Memory is orderable in 16 GB increments for customer use.
The system physical memory is the sum of all book memories. Not all books need to contain the same amount of memory, and not all installed memory is necessarily configured for use.
Memory sizes
The minimum orderable amount of usable memory for all models is 16 GB. Memory upgrades
are available in 16 GB increments:
Physically, the memory cards are organized as follows:
Within a book, memory is organized in two rows (banks) of four memory cards. Since book memory is organized in up to four Processor Memory Arrays (PMAs) and since one memory card only encompasses half a PMA, eight memory cards are needed for a full book with 128 GB.
A book always contains a minimum of four memory cards. Memory cards come in three sizes:
– 4 GB (512 Mb DRAMs)
– 8 GB (512 Mb, or 1 Gb DRAMs)
– 16 GB (1 Gb DRAMs)
Within a book, different memory card sizes can be plugged as long as the DRAM sizes are the same. Not all books necessarily need to have the same amount of physical memory installed.
A book may have more memory installed than enabled. The excess amount of memory can be installed by a Licensed Internal Code code load (sometimes called dial-a-Gig) when required by the installation.
On initial installation, the amount of physical memory in a given model is nearest to the smallest possible size. An example of this, for a z9 EC Model S08, is shown in Table 2-1.
Memory upgrades are satisfied from already installed unused memory capacity until exhausted. When no more unused memory is available from the installed memory cards, cards have to be upgraded to a higher capacity, or the addition of a book with additional memory is necessary.
Figure 2-2 shows examples of memory configurations (all possible combinations up to 128 GB are shown). It shows that an z9 EC Model S08 may have 16 GB of usable memory out of a minimum of 16 GB physically installed, and that an z9 EC Model S38, though unlikely, may have 16 GB of usable memory out of a minimum of 64 GB physical memory.
When activated, a logical partition can use memory resources located in any book. No matter in which book the memory resides, a logical partition has access to that memory if so allocated. Despite the book structure, the z9 EC is still a Symmetric Multi-Processor (SMP).
E Memory upgrade is concurrent when it requires no change of the physical memory cards. E A memory card change is disruptive when no use is made of Enhanced Book Replacement.
Chip sparing
Chip sparing is implemented by the use of X4 DRAMs across eight DIMMs where eight DIMMs make up one PMA. This results in four spares per PMA with Chipkill. Chipkill is an advanced error correction code that corrects multi bit memory errors.
Memory upgrades
For a model upgrade that results in the addition of a book, the minimum memory increment is added to the system. Remember, the minimum physical memory size in a book is 16 GB. During a model upgrade, the addition of a book is a concurrent operation. The addition of the physical memory that is in the added book is also concurrent. If all or part of the additional memory is enabled for installation use, it becomes available to an active logical partition if this partition has reserved storage defined (see 2.5.1, “Reserved storage” on page 83, for more detailed information). Or, it may be used by an already defined logical partition that is activated after the memory addition.
Book replacement and memory
With Enhanced Book Availability as supported for z9 EC (see “Enhanced Book Availability” on page 37), having sufficient resources available, to accommodate resources that are lost when a book is removed for upgrade or repair, is needed. Removal of a book most of the time results in the removal of active memory. With the Flexible Memory option (see “Flexible Memory option” on page 33) it is possible to evacuate the affected memory and reallocate its use elsewhere in the system. This requires additional available memory to compensate for the memory lost with the removal of the book.
Flexible Memory option
With the Flexible Memory option, sufficient inactive memory resources are made available for use when replacing a book. When ordering memory for a z9 EC, additional flexible memory can be specified. For example, on a z9 EC Model S18 this results in doubling the purchased amount for normal use. This assures that the content of the memory in the book to be removed can be moved to the excess memory in the other book. Flexible memory must be purchased but cannot be used for normal every day use. For that reason a different purchase price for the flexible memory is offered to increase the overall availability of the system.
In Table 2-3 the physical memory requirements for high availability for a two-book system are shown. The table does not show a complete list of all options. Card combinations up to 128 GB are shown.
