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| <div class="docbook"><div class="navheader"><table summary="Navigation header" width="100%"><tr><th align="center" colspan="3">9.6. Flow to Disk</th></tr><tr><td align="left" width="20%"><a accesskey="p" href="Java-Broker-Runtime-Close-Connection-When-No-Route.html">Prev</a> </td><th align="center" width="60%">Chapter 9. Runtime</th><td align="right" width="20%"> <a accesskey="n" href="Java-Broker-Runtime-Consumers.html">Next</a></td></tr></table><hr /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="Java-Broker-Runtime-Flow-To-Disk"></a>9.6. Flow to Disk</h2></div></div></div><p>Flow to disk limits the amount of <a class="link" href="Java-Broker-Runtime-Memory.html" title="9.11. Memory">direct and heap memory</a> |
| that can be occupied by messages. Once this |
| limit is reached any new transient messages and all existing transient messages will be |
| transferred to disk. Newly arriving transient messages will continue to go to the disk until the |
| cumulative size of all messages falls below the limit once again.</p><p>By default the Broker makes 75% of the max direct available memory for messages. This memory is |
| divided between all the queues across all virtual hosts defined on the Broker with a percentage |
| calculated according to their current queue size. These calculations are refreshed periodically |
| by the housekeeping cycle.</p><p>For example if there are two queues, one containing 75MB and the second 100MB messages |
| respectively and the Broker has 1GB direct memory with the default of 75% available for messages. |
| The first queue will have a target size of 320MB and the second 430MB. Once 750MB is taken by |
| messages, messages will begin to flow to disk. New messages will cease to flow to disk when |
| their cumulative size falls beneath 750MB.</p><p>Flow to disk is configured by Broker context variable |
| <code class="literal">broker.flowToDiskThreshold</code>. It is expressed as a size in bytes and defaults |
| to 75% of the JVM maximum heap size.</p></div><div class="navfooter"><hr /><table summary="Navigation footer" width="100%"><tr><td align="left" width="40%"><a accesskey="p" href="Java-Broker-Runtime-Close-Connection-When-No-Route.html">Prev</a> </td><td align="center" width="20%"><a accesskey="u" href="Java-Broker-Runtime.html">Up</a></td><td align="right" width="40%"> <a accesskey="n" href="Java-Broker-Runtime-Consumers.html">Next</a></td></tr><tr><td align="left" valign="top" width="40%">9.5. Closing client connections on unroutable mandatory messages </td><td align="center" width="20%"><a accesskey="h" href="Apache-Qpid-Broker-J-Book.html">Home</a></td><td align="right" valign="top" width="40%"> 9.7. Consumers</td></tr></table></div></div> |
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