114 lines
7.6 KiB
HTML
114 lines
7.6 KiB
HTML
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<title>Scenario: Hot-backup environment</title>
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</head>
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<body id="rzakihotbackup"><a name="rzakihotbackup"><!-- --></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">Scenario: Hot-backup environment</h1>
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<div><p>In this scenario, the remote journaling environment uses a hot-backup
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application that causes JKLINT2 to replace JKLINT in the case that JKLINT
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has a failure.</p>
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<p>A <span class="uicontrol">hot-backup application</span> typically performs the
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following:</p>
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<ol><li>If the primary system fails, it performs a switch-over to the backup system.
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This function then logically promotes the backup system to assume the role
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of the primary system.</li>
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<li>After the failed primary system is restarted, it performs a switch-back
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operation so that the primary system can again assume the role of the primary
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system.</li>
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</ol>
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<p>A <span class="uicontrol">hot-backup application apply</span> defines the part
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of a hot-backup application that actually performs the replay operations to
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the data replica. This usually occurs on the backup system when maintaining
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a data replica.</p>
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<p>The following figure describes a typical remote journal environment that
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is used for hot-backup purposes. The following occurs in this illustration:</p>
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<ul><li>Server JKLINT is the primary server while JKLINT2 is the backup server.</li>
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<li>Server JKLINT journals objects to local journal JKLB1/JRN.</li>
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<li>Changes to those journaled objects are also journaled to remote journal
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JLB2/JRN on server JKLINT2.</li>
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<li>On JKLINT2 a hot backup-apply replays changes to the data replica. When
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the hot backup-apply replays these changes, JKLINT2 journals the changes to
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its own local journal, JLB1/JRN.</li>
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<li>If JKLINT fails, JKLINT2 assumes the role of primary server and all local
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journaling of changes to the data replica (now acting as the original data)
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continue on JKLINT2's local journal, JLB1/JRN.</li>
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<li>When it is time to switch the role of primary server back to JKLINT, JKLINT2
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sends changes from its local journal, JLB1/JRN, to remote journal JLB2/JRN
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on server JKLINT (the transport from JKLINT2 to JKLINT is only used for this
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purpose).</li>
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<li>JKLINT then uses its remote journal, JLB2/JRN, to replay changes to the
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original data.</li>
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</ul>
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<div class="section"><h4 class="sectiontitle">Typical hot-backup environment with remote journal function</h4><br /><img src="rzaki515.gif" alt="Typical hot-backup environment with remote journal function" /><br /></div>
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<div class="section"><h4 class="sectiontitle">How to establish the hot-backup environment</h4><p>The
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steps to establish a hot-backup environment the are the same as establishing
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data replication environment except for this additional last step:</p>
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<p>Sharon
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also establishes a remote journal JKLINT that is associated with the local
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journal that she creates on JKLINT2. This remote journal receives or retrieves
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the journaled changes that are made when JKLINT2 assumes the role of the primary
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system. This local journal and remote journal pair will only be used when
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replicating changes back to the original data. During normal run-time processing,
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the remote journal, JLB2/JRN, that is defined on JKLINT is not active. When
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it is not active, it is not receiving or retrieving journal entries from the
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local journal, JLB1/JRN, on JKLINT2.</p>
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</div>
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<div class="section"><h4 class="sectiontitle">Normal run-time environment for the hot-backup environment</h4>The
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details for run-time environment for the hot-backup environment is the same
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as the data replication environment.</div>
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<div class="section"><h4 class="sectiontitle">Hot-backup recovery if JKLINT fails</h4><p>If you use a
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hot-backup application where the logical ownership of the data is given to
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JKLINT2, recovery is more complicated. In this case, the hot-backup application
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logically promotes JKLINT to assume the role of the primary system. Recovery
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is more complicated because after JKLINT has completed its IPL, the remote
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journal function catch-up phase from the local journal on system JKLINT to
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the remote journal on system JKLINT2 will always allow a resynchronization
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of the two sets of data.</p>
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<p><span class="uicontrol">Data resynchronization</span> is
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recovery processing that is performed during switch-back processing by a hot-backup
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application apply. This processing ensures that the original data is consistent
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with the data replica, and contains all the correct changes. The main objective
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of this, besides assuring data consistency, is to eliminate re-priming the
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original data from the data replica.</p>
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<p>For details on recovering a hot-backup
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environment see Scenario: Recovery for remote journaling.</p>
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</div>
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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="rzakirscenarios.htm" title="These scenarios describe the possible ways that JKL Toy Company can use remote journal management. JKL Toy Company uses the server JKLINT as their web server.">Scenarios: Remote journal management and recovery</a></div>
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</div>
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<div class="relinfo"><strong>Related information</strong><br />
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<div><a href="rzakirdatarep.htm" title="In this scenario, JKLINT and JKLINT2 use remote journaling for data replication purposes only.">Scenario: Data replication environment for remote journals</a></div>
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<div><a href="rzakirecovery.htm" title="This scenario describes a hot-backup environment in which the local system, JKLINT fails. It is necessary to restore the local system, and synchronize it with the remote system, JKLINT2.">Scenario: Recovery for remote journaling</a></div>
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</div>
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</div>
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