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<title>Journal management for distributed relational databases</title>
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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">Journal management for distributed relational databases</h1>
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<div><p>Journal management can be used as a part of the backup and recovery
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strategy for relational databases and indexes.</p>
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<div class="section"><p><span class="keyword">iSeries™</span> journal
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support provides an audit trail and forward and backward recovery. Forward
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recovery can be used to take an older version of a table and apply changes
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logged in the journal to the table. Backward recovery can be used to remove
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changes logged in the journal from the table.</p>
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</div>
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<div class="section"><p>When a collection is created, a journal and an object called a
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journal receiver are created in the collection. Improved performance is gained
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when the journal receiver is on a different ASP from the tables.
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Placing the collection on a user ASP places the tables and journal and journal
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receivers all in the same user ASP. There is no gain in performance there.
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Creating a new journal receiver in a different ASP (used just for this journal's
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journal receivers) and attaching it with the <span class="cmdname">Change Journal (CHGJRN)</span> command
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will get the next server generated journal receivers all in the other user
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ASP, and then the user will see improved performance.</p>
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</div>
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<div class="section"><p>When a table is created, it is automatically journaled to the
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journal SQL created in the collection. You are then responsible for using
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the journal functions to manage the journal, journal receivers, and the journaling
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of tables to the journal. For example, if a table is moved into a collection,
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no automatic change to the journaling status occurs. If a table is restored,
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the normal journal rules apply. That is, if a table is journaled when it is
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saved, it is journaled to the same journal when it is restored on that server.
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If the table is not journaled at the time of the save, it is not journaled
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at restore time. You can stop journaling on any table using the journal functions,
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but doing so prevents SQL operations from running under commitment control.
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SQL operations can still be performed if you have specified COMMIT(*NONE),
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but this does not provide the same level of integrity that journaling and
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commitment control provide.</p>
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</div>
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<div class="section"><p>With journaling active, when changes are made to the database,
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the changes are journaled in a journal receiver before the changes are made
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to the database. The journal receiver always has the latest database information.
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All activity is journaled for a database table regardless of how the change
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was made.</p>
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</div>
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<div class="section"><p>Journal receiver entries record activity for a specific row (added,
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changed, or deleted), and for a table (opened, table or member saved, and
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so on). Each entry includes additional control information identifying the
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source of the activity, the user, job, program, time, and date.</p>
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</div>
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<div class="section"><p>The server journals some file-level changes, including moving
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a table and renaming a table. The server also journals member-level changes,
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such as initializing a physical file member, and server-level changes, such
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as initial program load (IPL). You can add entries to a journal receiver to
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identify significant events (such as the checkpoint at which information about
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the status of the job and the server can be journaled so that the job step
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can be restarted later) or to help in the recovery of applications.</p>
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</div>
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<div class="section"><p>For changes that affect a single row, row images are included
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following the control information. The image of the row after a change is
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made is always included. Optionally, the row image before the change is made
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can also be included. You control whether to journal both before and after
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row images or just after row images by specifying the IMAGES parameter on
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the <span class="cmdname">Start Journal Physical File (STRJRNPF)</span> command.</p>
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</div>
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<div class="section"><p>All journaled database files are automatically synchronized with
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the journal when the server is started (IPL time) or during the vary on of
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an independent ASP. If the server ended abnormally, or the independent ASP
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varied off abnormally, some database changes might be in the journal, but
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not yet reflected in the database itself. If that is the case, the server
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automatically updates the database from the journal to bring the tables up
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to date.</p>
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</div>
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<div class="section"><p>Journaling can make saving database tables easier and faster.
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For example, instead of saving entire tables every day, you can save the journal
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receivers that contain the changes to the tables. You can still save the entire
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tables on a regular basis. This method can reduce the amount of time it takes
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to perform your daily save operations.</p>
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</div>
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<div class="section"><p>The <span class="cmdname">Display Journal (DSPJRN)</span> command can be
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used to convert journal receiver entries to a database file. Such a file can
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be used for activity reports, audit trails, security, and program debugging.</p>
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</div>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="rbal1indexrec.htm">Index recovery</a></strong><br />
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An index describes the order in which rows are read from a table. When indexes are recorded in the journal, the server can recover the index to avoid spending a significant amount of time rebuilding indexes during the IPL that follows an abnormal server end or during the vary on of an independent ASP after an abnormal vary off.</li>
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<li class="ulchildlink"><strong><a href="rbal1tblindex.htm">Design tables to reduce index rebuilding time</a></strong><br />
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Table design can also help reduce index recovery time.</li>
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<li class="ulchildlink"><strong><a href="rbal1smapp2.htm">System-managed access-path protection</a></strong><br />
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System-managed access-path protection (SMAPP) provides automatic protection for access paths.</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rbal1recovsupp.htm" title="Failures that can occur on a computer server are a server failure (when the entire server is not operating); a loss of the site due to fire, flood, or similar catastrophe; or the damage or loss of an object. For a distributed relational database, a failure on one server in the network prevents users across the entire network from accessing the relational database on that server.">Recovery support for a distributed relational database</a></div>
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</div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="../rzaki/rzakikickoff.htm">Journal management</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="../cl/chgjrn.htm">Change Journal (CHGJRN) command</a></div>
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<div><a href="../cl/dspjrn.htm">Display Journal (DSPJRN) command</a></div>
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<div><a href="../cl/strjrnpf.htm">Start Journal Physical File (STRJRNPF) command</a></div>
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</div>
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</div>
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