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Another useful tool for monitoring database activity is the
<code class="structname">pg_locks</code> system table. It allows the
database administrator to view information about the outstanding
locks in the lock manager. For example, this capability can be used
to:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
View all the locks currently outstanding, all the locks on
relations in a particular database, all the locks on a
particular relation, or all the locks held by a particular
<span class="productname">PostgreSQL</span> session.
</p></li><li class="listitem"><p>
Determine the relation in the current database with the most
ungranted locks (which might be a source of contention among
database clients).
</p></li><li class="listitem"><p>
Determine the effect of lock contention on overall database
performance, as well as the extent to which contention varies
with overall database traffic.
</p></li></ul></div><p>
Details of the <code class="structname">pg_locks</code> view appear in
<a class="xref" href="view-pg-locks.html" title="52.73. pg_locks">Section 52.73</a>.
For more information on locking and managing concurrency with
<span class="productname">PostgreSQL</span>, refer to <a class="xref" href="mvcc.html" title="Chapter 13. Concurrency Control">Chapter 13</a>.
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