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<h2 class="title" style="clear: both"><a id="admin-locking"></a>Managing the Locking Subsystem</h2>
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<p>
Whenever the BDB SQL interface reads from or writes to the
database, the underlying Berkeley DB code must acquire
locks. These locks represent a finite resource. For
most installations, you should never have to worry
about the locking resources available to Berkeley DB
because the default values are appropriate
for most applications.
</p>
<p>
However, if your application is using an extremely large number of
threads that are all simultaneously accessing your data, then
you might have to increase your locking resources. Similarly,
if your database contains a very large number of tables that
you are accessing using one or more simultaneous threads or
processes, then you might also need to increase your locking resources.
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<p>
On the other hand, if you are using the BDB SQL interface on devices with
extremely limited resources, then you might want to reduce
your locking resources.
</p>
<p>
All of these values must be configured before your
environment is first created. To change these values
after environment creation time, you must re-create the
environment. See
<a class="xref" href="using_dbconfig.html" title="The DB_CONFIG File">The DB_CONFIG File</a>
for more information.
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<p>
The maximum locking values that you can manage, and the
<code class="literal">DB_CONFIG</code> parameter that you use to manage
that value, are:
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<p>
The maximum number of lockers
supported by the environment. This value is used by
the environment when it is opened to estimate the amount
of space that it should allocate for various internal
data structures. By default, 2,000 lockers are
supported.
</p>
<p>
The maximum number of lockers corresponds roughly
to the maximum number of concurrent transactions in
the system.
</p>
<p>
To configure this value, use the
<code class="literal">set_lk_max_lockers</code> DB_CONFIG parameter.
See the <a class="ulink" href="http://download.oracle.com/docs/cd/E17076_02/html/api_reference/C/BDB-C_APIReference.pdf" target="_top">Berkeley DB C API
</a>
for details.
</p>
</li>
<li>
<p>
The maximum number of locks supported by the environment.
By default, 10,000 locks are supported.
</p>
<p>
To configure this value, use the
<code class="literal">set_lk_max_locks</code> DB_CONFIG parameter.
See the <a class="ulink" href="http://download.oracle.com/docs/cd/E17076_02/html/api_reference/C/BDB-C_APIReference.pdf" target="_top">Berkeley DB C API
</a>
for details.
</p>
</li>
<li>
<p>
The maximum number of locked objects supported by the environment.
By default, 10,000 objects can be locked.
</p>
<p>
To configure this value, use the
<code class="literal">set_lk_max_objects</code> DB_CONFIG parameter.
See the <a class="ulink" href="http://download.oracle.com/docs/cd/E17076_02/html/api_reference/C/BDB-C_APIReference.pdf" target="_top">Berkeley DB C API
</a>
for details.
</p>
</li>
</ul>
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<p>
Note that when you are using the BDB SQL interface, the default
values provided in the previous list are different from the
default values used by Berkeley DB in general. For Berkeley DB in
general, the defaults for all these values are set to 1,000.
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