Reconfiguring vPars v6 memory with zero downtime

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Patch requirement
vPar version 6.2 must have the patch PHKL_43308 installed to use the online memory migration feature. This patch will
be automatically installed as part of the HP-UX 11i v3 March 2013 update. If you are running an HP-UX11i v3 version prior
to March 2013 update on your vPar, you must install this patch.
About vPar online memory migration
Online addition and deletion of memory is supported on vPars v6 starting with the HP-UX vPars and Integrity VM v6.2
release. This means that memory can be added and deleted from a live vPar without needing a reboot.
When memory is added to a live vPar,
• The VSP congures and presents the requested memory from the vPar/VM memory pool to the vPar.
• The HP-UX kernel in the vPar discovers and integrates the new memory pages. Subsequently, applications can use the
new memory.
NOTE
The VSP attempts to obtain memory from the vPar/VM memory pool, based on the most favourable NUMA
characteristics of the vPar. There are no manual controls to change memory selection.
When memory is to be deleted from a live vPar,
• The HP-UX kernel in the vPar selects the memory pages to evacuate and moves the contents to other available free
pages and then frees those memory pages.
• The VSP marks the memory as free, returns the memory back to the vPar/VM memory pool and this memory can be
assigned to other vPars.
Base and oating memory
In HP-UX, portions of memory that contain kernel code and certain kernel data structures cannot be evacuated. While
allocating memory during boot or during run-time, the HP-UX kernel needs to know in advance what memory to use for
kernel data structures as those cannot be evacuated. To aid the HP-UX kernel in this dierentiation, the vPars software
subdivides memory into two types: base memory and oating memory.
Base memory
This memory used by the vPar HP-UX kernel for critical data structures. You can increase the amount of base memory of
a live vPar but you cannot decrease it.
Floating memory
This is typically used for user applications. You can either increase or decrease oating memory from a live vPar.
NOTE
The oating memory that is deleted from one vPar can be allocated to another vPar as base or oating memory. The
notion of base and oating memory is only applicable within the vPar context.
Technical white paper | HP-UX vPars and Integrity VM v6.2