Reserved Expanded Storage; Expanded Storage Origins - IBM Z9 Planning Manual

v Initial expanded storage is reconfigurable (can be configured offline or online by
the control program) for ESA/390 LPs that have no reserved expanded storage
defined.
v The initial amount of expanded storage can be zero when the reserved expanded
storage is nonzero.
v A request for an initial expanded storage amount can be satisfied only when both
sufficient expanded storage addressability and sufficient physical storage are
available.
Also, there must be a large enough contiguous central storage addressability
range to back the initial expanded storage amount. This range will be chosen by
the system in a top-down first-fit algorithm. It is not user-specifiable. If a large
enough central storage addressability range is not available to satisfy the initial
expanded storage request, LP activation will fail.

Reserved Expanded Storage

v Only LPs that specify a reserved expanded storage origin can be allocated
storage within the reserved expanded storage for another LP. Reserved
expanded storage can only overlap LPs that have an expanded storage origin
specified.
v Expanded reserved storage is contiguous to and above the initial amount of
expanded storage.
v ESA/390 and Linux-Only LPs can have nonzero amounts for this parameter.
Coupling facility LPs cannot have reserved expanded storage amounts.
v The reserved amounts of expanded storage defines the additional amounts of
storage that can become available to an LP when no other activated LP has this
reserved storage online. Reserved storage amounts are always offline after LP
activation.
v For reserved expanded storage, all of the reserved expanded storage must be
available to configure any reserved expanded storage online.
v Reserved expanded storage for an LP can be specified with or without specifying
an origin.
Also, there must be a large enough contiguous central storage addressability
range to back the reserved expanded storage amount. This range will be chosen
by the system in a top-down first-fit algorithm. It is not user-specifiable. If a large
enough central storage addressability range is not available to satisfy the
reserved storage request, the element cannot be brought online.

Expanded Storage Origins

v The origin for expanded storage defines the starting megabyte where the
expanded storage addressability range begins for the LP. If enough expanded
storage is not available to satisfy the initial request starting at this origin, LP
activation will fail. If there is no initial amount of expanded storage defined, the
reserved amount of expanded storage starts at this origin.
v There must be enough contiguous expanded storage addressability to fit the
reserved amounts, but the reserved addressability can be in use by other LPs
(that have expanded storage origins specified) at the time the LP is activated.
v For expanded storage, the specification of the origin parameter provides the only
way to overlap storage definitions. For example, the reserved storage definition
for one LP can overlap the storage definition of another LP when the origin
parameter is specified for both LPs. The total amount of expanded storage
addressability that can be used to map expanded storage for LPs is at least
Chapter 3. Determining the Characteristics of Logical Partitions
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