110 lines
7.4 KiB
HTML
110 lines
7.4 KiB
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<meta name="DC.Title" content="Application considerations for independent disk pools" />
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<title>Application considerations for independent disk pools</title>
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</head>
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<body id="rzalyapplications"><a name="rzalyapplications"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Application considerations for independent disk pools</h1>
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<div><p>When you are designing or restructuring your application environment for
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use with independent disk pools, there are several things you should be aware
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of. A few of these considerations include the existence of multiple databases,
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the objects that can and cannot be created in an independent disk pool, how
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the library list works, and the placement of programs and data in the correct
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database.</p>
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<p>When a primary independent disk pool is made available for the first time,
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a new database with the same name is also generated by default. See <a href="rzalydatabases.htm">Independent disk pools with distinct databases</a> for more information.
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If you write an application to access files and libraries in a disk pool group,
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you must specify how to access that specific database. Some of your options
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include:</p>
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<ul><li>Use the Set ASP Group <a href="../cl/setaspgrp.htm">(SETASPGRP)</a> command.</li>
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<li>In an <a href="../db2/rbafzmst02.htm">SQL
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environment</a>, use CONNECT to specify the right database. To achieve
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the fastest performance, make sure that the database to which you perform
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an SQL CONNECT operation corresponds with your current library namespace.
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You may need to use the SETASPGRP command first to achieve this. If the SQL
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CONNECT function is not operating within the same library namespace, the application
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uses Distributed Relational Database Architecture<sup>(TM)</sup> support,
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which can affect performance.</li>
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<li>Use the Change Job Description (<a href="../cl/chgjobd.htm">CHGJOBD</a>) command to set the initial ASP group in the
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job description for a user profile. </li>
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</ul>
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<p>As you write applications that create objects, you must know which objects
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are supported. See <a href="rzalysupportedunsupportedobjects.htm">Supported and unsupported object types</a>. If your application uses the Create Library (<a href="../cl/crtlib.htm">CRTLIB</a>) command, you must specify CRTLIB
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ASP(*ASPDEV) ASPDEV(<em>asp-device-name</em>). If you do not specify these parameters
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for CRTLIB, the library is created in the system disk pool by default. However,
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if you use the SQL statement, CREATE COLLECTION, the default for the IN ASP
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clause is the current library namespace.</p>
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<p>When you are operating in an SQL environment, permanent SQL
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objects cannot span independent disk pool boundaries. For example, you cannot
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create a view of an independent disk pool object in the system disk pool.
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This action fails. </p>
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<p>A similar concept is true for commitment control with independent disk
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pools. If you are connected to an independent disk pool relational database,
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you cannot make committable changes against objects in any other disk pool.
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When commitment control is active, you have read-only access. You can make
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committable changes against QTEMP, but you might receive error messages.
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</p>
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<p>It might also be helpful to understand how the library list works when
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independent disk pools are implemented. When the library list includes QSYS,
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QSYS2, or SYSIBM, the <a href="rzalymultiplesystemlibraries.htm">Multiple system libraries</a> in the independent disk pool (QSYSnnnnn, QSYS2nnnnn,
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SYSIBnnnnn) are searched before the libraries in the system disk pool. If
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the object is found in the independent disk pool, the system disk pool will
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not be searched. In addition, if you switch to a different disk pool group,
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any libraries that were in the previous library list are removed from the
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current library list. </p>
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<p>You also need to carefully consider where you store data, applications,
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and application exit programs. It is recommended that data should be stored
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in independent disk pools. If your independent disk pools are dedicated to
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the server, it might work to store applications and exit programs in the
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system database so that they are always accessible, regardless of what disk
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pool group is associated with a job. If you use the independent disk pool
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in a clustered environment, you must remember that when the disk pool is
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switched to another server, the exit program must be available there as well.
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In this case, it may be more appropriate to store the applications and exit
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programs in the independent disk pool. Remember that the cluster resource
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group (CRG) exit program cannot exist in an independent disk pool.</p>
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<p id="rzalyapplications__v5r3"><a name="rzalyapplications__v5r3"><!-- --></a>If you are using the independent disk pool in a clustered environment,
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you must also remember that the user profiles are not stored in the independent
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disk pool. They are kept in the system disk pool. If an independent disk pool
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fails over or is switched to another node where the user profile does not
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currently exist, a user profile might be created on the new node. For a user
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profile to be created, it must own objects on the switchable disk pool, be
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the primary group of objects on the switchable disk pool, or be privately
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authorized to objects on the switchable disk pool. The new user profile has
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no special authorities and the password is set to *NONE.</p>
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<p>Authorization lists may also be created. For an authorization
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list to be created, it must not currently exist on the target system and it
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must secure an object on the switchable disk unit. When an authorization list
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is created, the public authority is set to *EXCLUDE, and no users are given
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private authority to it.</p>
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<p>If you are operating in a clustered environment, see <a href="../rzaig/rzaigapplications.htm">Cluster applications</a> for more information
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about writing and implementing highly available applications within your cluster.</p>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzalyplan.htm">Plan for independent disk pools</a></div>
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</div>
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</div>
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</body>
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</html>
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