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<h1 class="topictitle1">Independent disk pool terminology</h1>
<div><p>As you work with independent disk pools, you need to become familiar with
the following terms. For more terms and concepts, you can access the information
center <a href="../rzaat/as4glos.htm">glossary</a>. </p>
<p><span class="uicontrol">Important:</span> The terms <span class="uicontrol">independent auxiliary
storage pool (ASP)</span> and <span class="uicontrol">independent disk pool</span> are
synonymous.</p>
<dl><dt class="dlterm">active state</dt>
<dd>In geographic mirroring, pertaining to
the configuration state of a mirror copy that indicates geographic mirroring
is being performed if the disk pool is available.</dd>
<dt class="dlterm">asynchronous</dt>
<dd>In geographic mirroring, pertaining to the mode where the program issuing
the update waits until the operation is completed on the production copy and
received for processing on the target system.</dd>
<dt class="dlterm"><strong>cluster</strong></dt>
<dd>A collection of complete systems that work together to provide a single,
unified computing capability. An iSeries™ cluster is made up of only iSeries servers
and is required when implementing switchable independent disk pools.</dd>
<dt class="dlterm"><strong>cluster resource group (CRG)</strong></dt>
<dd>A collection of related cluster resources that defines actions to be taken
during a switchover or failover operation of the access point of resilient
resources. These resilient resources include applications, data, and devices.
The group describes a recovery domain and supplies the name of the cluster
resource group exit program that manages the movement of an access point.
A device CRG contains a list of devices, such as independent disk pools.
The independent disk pools can reside on a switchable entity that can be either
an expansion unit (frame/unit) or an IOP. In iSeries Navigator, a device cluster resource
group is referred to as a switchable hardware group. </dd>
<dt class="dlterm">cross-site mirroring (XSM)</dt>
<dd>A feature of i5/OS™ High Available Switchable Resources
(Option 41) that provides geographic mirroring and the services to switch
over or automatically cause a failover to a mirror copy, potentially at another
location, in the event of an outage at the primary location.</dd>
<dt class="dlterm">data port services</dt>
<dd>The generic transport mechanism used by geographic mirroring to send updates
from the source system that owns the production copy to the target system
that owns the mirror copy.</dd>
<dt class="dlterm">detach</dt>
<dd>In geographic mirroring, to disassociate a mirror copy from the production
copy in order to use the mirror copy for a separate operation, such as to
save data, to run reports, or to perform data mining. Detaching a mirror
copy suspends geographic mirroring.</dd>
<dt class="dlterm">detached mirror copy</dt>
<dd>A detached mirror copy of an independent
disk pool is a mirror copy that is disassociated from the production copy
in a geographic mirroring environment.</dd>
<dt class="dlterm"><strong>device description</strong></dt>
<dd>An object that contains information describing a particular device or
logical unit (LU) that is attached to the system. A device description is
a description of the logical connection between two LUs (local and remote
locations). The system-recognized identifier for the object type is *DEVD. </dd>
<dt class="dlterm"><strong>device domain</strong></dt>
<dd>A device domain is a collection of cluster nodes that share device resources,
such as independent disk pools. For independent disk pools, the resources
are: virtual addresses, disk pool numbers and disk unit numbers. An independent
disk pool can only be accessed by the nodes in one device domain. </dd>
<dt class="dlterm"><strong>disk pool</strong> </dt>
<dd>An auxiliary storage pool that contains only disk units.</dd>
<dt class="dlterm"><strong>disk pool group</strong></dt>
<dd>Made up of a primary disk pool and zero or more secondary disk pools,
each of which are independent in regard to data storage, but combine to act
as one entity.</dd>
<dt class="dlterm"><strong>disk unit</strong> </dt>
<dd>A physical enclosure containing one or more disk drives. </dd>
<dt class="dlterm"><strong>expansion unit</strong></dt>
<dd>A feature that can be connected to a system unit to provide additional
storage and processing capacity.</dd>
<dt class="dlterm"><strong>failover</strong> </dt>
<dd>A cluster event where the primary database server or application server
switches over to a backup system due to the failure of the primary server</dd>
<dt class="dlterm">geographic mirroring</dt>
<dd>A subfunction of cross-site mirroring (XSM) that generates a mirror image
of an independent disk pool on a system, which is (optionally) geographically
distant from the originating site for availability or protection purposes.</dd>
<dt class="dlterm"><strong>HSL (high-speed link) loop</strong></dt>
<dd>The system-to-expansion unit connectivity technology that is required
to use switchable independent disk pools residing on an expansion unit (frame/unit).
The servers and expansion unit in a cluster using resilient devices on an
external expansion unit must be on an HSL loop connected with HSL cables.</dd>
<dt class="dlterm"><strong>independent disk pool</strong> </dt>
<dd>Disk pools 33 to 255. One or more storage units that are defined from
the disk units or disk-unit subsystems that make up addressable disk storage.
An independent disk pool contains objects, the directories and libraries that
contain the objects, and other object attributes such as authorization ownership
attributes. An independent disk pool can be made available (varied on) and
made unavailable (varied off) without restarting the system. An independent
disk pool can be either a) privately connected to a single system b) switchable
among multiple systems in a clustering environment or c) duplicated at another
site by geographic mirroring. Synonymous with <em>independent auxiliary storage
pool (ASP)</em>.</dd>
<dt class="dlterm">insync</dt>
<dd>In geographic mirroring, pertaining to the mirror copy data state that
indicates that the production and mirror copy have exactly the same contents.</dd>
<dt class="dlterm"><strong>library namespace</strong></dt>
<dd>An attribute that can be set for the current thread. The library namespace
is the set of objects and libraries that can be accessed in any independent
disk pools in a disk pool group plus the libraries in the system disk pool
and basic user disk pools (ASPs 2-32) using the regular library-qualified
object name syntax. The Set Auxiliary Storage Pool Group (SETASPGRP) command
sets the auxiliary storage pool (ASP) group for the current thread. </dd>
<dt class="dlterm">mirror copy</dt>
<dd>In geographic mirroring, an independent disk pool that is being geographically
mirrored so that it is a replica of the production copy of the independent
disk pool. If a switchover or failover causes the system that owns the mirror
copy to become the current primary node, the mirror copy becomes the production
copy of the independent disk pool. The mirror copy has current data only when
geographic mirroring is active.</dd>
<dt class="dlterm">mirror copy state</dt>
<dd>In geographic mirroring, the geographic mirroring state of the mirror
copy; for example, active, resume pending, resuming, and suspended.</dd>
<dt class="dlterm">mirror copy data state</dt>
<dd>In geographic mirroring, the current status of the data that is being
geographically mirrored; for example, insync, usable, and unusable.</dd>
<dt class="dlterm"><strong>primary disk pool</strong></dt>
<dd>An independent disk pool that defines a collection of directories and
libraries and may have other secondary disk pools associated with it. A primary
disk pool also defines a database for itself and other disk pools that may
be added in its disk pool group. Primary disk pools can only be implemented
on V5R2 or later of OS/400<sup>®</sup>. </dd>
<dt class="dlterm">production copy</dt>
<dd>In geographic mirroring, the independent disk pool to which all production
operations are directed. All disk write operations are directed here first
and are then replicated to the mirror copy of the independent disk pool. The
production copy always has current data.</dd>
<dt class="dlterm">reattach</dt>
<dd>In geographic mirroring, to reassociate
the detached mirror copy with its production copy after user operations on
the detached mirror copy are completed. When the detached mirror copy is reattached,
it is automatically synchronized to match the production copy again. All data
on the detached mirror copy is cleared before it is reattached to the production
copy.</dd>
<dt class="dlterm">resume </dt>
<dd>In geographic mirroring, to start performing
geographic mirroring again after it is suspended.</dd>
<dt class="dlterm">resume pending state</dt>
<dd>In geographic mirroring, pertaining to
the configuration state of a mirror copy that indicates that geographic mirroring
requires synchronization but that the disk pool is currently unavailable.
When the disk pool is made available, the mirror copy will be synchronized
with the current data from the production copy.</dd>
<dt class="dlterm">resuming state</dt>
<dd>In geographic mirroring, the configuration state of the mirror copy that
attempts to perform geographic mirroring and synchronization when the independent
disk pool is available. The mirror copy state is resuming when it is not
suspended or active.</dd>
<dt class="dlterm"><strong>secondary disk pool</strong></dt>
<dd>An independent disk pool that defines a collection of directories and
libraries and must be associated with a primary disk pool. Secondary disk
pools can only be implemented on V5R2 or later of OS/400. See </dd>
<dt class="dlterm">site</dt>
<dd>In cross-site mirroring, a location containing a node or nodes with access
to either the production copy or mirror copy. The sites can be in close proximity
or geographically dispersed.</dd>
<dt class="dlterm"><a name="rzalyterminology__v5r3"><!-- --></a>site primary node</dt>
<dd>In cross-site mirroring, a node that owns the independent disk pool, either
the production copy or mirror copy, at a particular site. The production-site
primary node is also the primary node for the cluster resource group. The
mirror-site primary node is a backup node in a cluster resource group.</dd>
<dt class="dlterm">source system</dt>
<dd>The system that currently owns the production
copy of an independent disk pool in a cross-site mirroring (XSM) environment.
The target system is a backup node in the cluster resource group and is the
mirror site primary node. Changes to the production copy of an independent
disk pool are replicated to the mirror copy of the independent disk pool that
exist on a backup node within the recovery domain.</dd>
<dt class="dlterm">suspend</dt>
<dd>In geographic mirroring, to temporarily
stop performing geographic mirroring. If the mirror copy contained usable
data when suspended, the mirror copy still contains usable, though possibly
outdated, data.</dd>
<dt class="dlterm">suspended state</dt>
<dd>In geographic mirroring, pertaining to the configuration state of the
mirror copy that does not attempt to perform geographic mirroring when the
independent disk pool is available. The mirror copy state is suspended when
it is not resuming or active.</dd>
<dt class="dlterm"><strong>switchable entity</strong></dt>
<dd>The physical resource containing the independent disk pools that can be
switched between systems in a cluster. This can be a expansion unit containing
disk units in a multiple system environment. This might also be an IOP containing
disk units in an LPAR environment. </dd>
<dt class="dlterm"><strong>switchover</strong></dt>
<dd>A cluster event where the primary database server or application server
switches over to a backup system due to the manual intervention from the
cluster management interface. </dd>
<dt class="dlterm"><img src="./delta.gif" alt="Start of change" />full synchronization<img src="./deltaend.gif" alt="End of change" /></dt>
<dd><img src="./delta.gif" alt="Start of change" />The geographic mirroring processing that copies data from the production
copy to the mirror copy. During synchronization the mirror copy contains
unusable data. When synchronization is completed, the mirror copy contains
usable data.<img src="./deltaend.gif" alt="End of change" /></dd>
<dt class="dlterm"><img src="./delta.gif" alt="Start of change" />partial synchronization<img src="./deltaend.gif" alt="End of change" /></dt>
<dd><img src="./delta.gif" alt="Start of change" />While the system is in a suspended state, changes made to the production
copy are not sent to the mirror copy. If the production copy is suspended
with tracking, any changes made to the production copy are instead tracked.
Once geographic mirror is resumed and partial synchronization is started,
those tracked changes are then sent to the mirror copy.<img src="./deltaend.gif" alt="End of change" /></dd>
<dt class="dlterm">synchronous</dt>
<dd>In geographic mirroring, pertaining to the mode of geographic mirroring
where the program that issues the update waits until the operation is completed
to disk on both the production copy and the mirror copy. This mode ensures
that once control is returned to the client, the operation is accurately reflected
on both the production copy and the mirror copy.</dd>
<dt class="dlterm"><strong>SYSBAS</strong></dt>
<dd>In the character-based interface, refers to the system disk pool 1 and
all configured basic disk pools 2 through 32. Independent disk pools 33 through
255 are not included.</dd>
<dt class="dlterm">target system</dt>
<dd>A system that currently owns a mirror copy of an independent ASP in a
cross-site mirroring (XSM) environment. Changes to the production copy of
an independent disk pool on the source system are replicated to the mirror
copy of the independent disk pool that exists on a target system.</dd>
<dt class="dlterm"><img src="./delta.gif" alt="Start of change" />tracking<img src="./deltaend.gif" alt="End of change" /></dt>
<dd><img src="./delta.gif" alt="Start of change" />A process that remembers changes that occur while geographic mirroring
is suspended. When geographic mirroring resumes the system only synchronizes
the tracked changes and does not perform a full synchronization.<img src="./deltaend.gif" alt="End of change" /></dd>
<dt class="dlterm"><strong>UDFS disk pool</strong></dt>
<dd> An independent disk pool that contains only user-defined file systems.
It cannot be a member of a disk pool group unless it is converted to a primary
or secondary disk pool.</dd>
<dt class="dlterm">unusable</dt>
<dd>In geographic mirroring, pertaining to the mirror copy data state that
indicates that the mirror copy contains incoherent data. This occurs: <ol><li>During synchronization because synchronization does not preserve the order
of writes.</li>
<li>When the system performs geographic mirroring in asynchronous mode.</li>
</ol>
<div class="note"><span class="notetitle">Note:</span> <img src="./delta.gif" alt="Start of change" />The mirror copy becomes usable during a vary-off of
the production copy of the independent disk pool.<img src="./deltaend.gif" alt="End of change" /></div>
</dd>
<dt class="dlterm">usable</dt>
<dd>In geographic mirroring, pertaining to the mirror copy data state that
indicates that the correct order of updates to the mirror copy from the production
copy is being preserved, but the mirror copy may be outdated. The usable mirror
copy data state occurs: <ol><li>When the system performs geographic mirroring in synchronous mode.</li>
<li>After successfully suspending geographic mirroring.</li>
<li>When mirror copy is successfully detached.</li>
</ol>
<div class="note"><span class="notetitle">Note:</span> <img src="./delta.gif" alt="Start of change" /><ol><li>The mirror copy becomes usable during a vary-off of the production copy
of the independent disk pool.</li>
<li>Number 1 and 2 do not apply during a synchronization.</li>
</ol>
<img src="./deltaend.gif" alt="End of change" /></div>
</dd>
<dt class="dlterm"> <strong>vary off</strong></dt>
<dd> To make an independent disk pool unavailable for its normal, intended
use. All of the primary and secondary disk pools in a disk pool group will
vary off together. Synonymous with <em>make unavailable</em>. </dd>
<dt class="dlterm"><strong>vary on</strong> </dt>
<dd>To make an independent disk pool available for its normal, intended use.
All of the primary and secondary disk pools in a disk pool group are varied
on together. Synonymous with <em>make available</em>. </dd>
</dl>
</div>
<div>
<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="rzalyconcepts.htm">Independent disk pools</a></div>
</div>
<div class="relinfo"><strong>Related information</strong><br />
<div><a href="rzalyiasptypes.htm">Types of disk pools</a></div>
<div><a href="rzalydiskpoolgroups.htm">Disk pool groups</a></div>
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