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From build...@apache.org
Subject svn commit: r1002502 - in /websites/production/activemq/content: cache/main.pageCache kahadb.html
Date Fri, 09 Dec 2016 14:22:33 GMT
Author: buildbot
Date: Fri Dec  9 14:22:33 2016
New Revision: 1002502

Log:
Production update by buildbot for activemq

Modified:
    websites/production/activemq/content/cache/main.pageCache
    websites/production/activemq/content/kahadb.html

Modified: websites/production/activemq/content/cache/main.pageCache
==============================================================================
Binary files - no diff available.

Modified: websites/production/activemq/content/kahadb.html
==============================================================================
--- websites/production/activemq/content/kahadb.html (original)
+++ websites/production/activemq/content/kahadb.html Fri Dec  9 14:22:33 2016
@@ -91,7 +91,7 @@
  </broker>
 
 </pre>
-</div></div><h3 id="KahaDB-KahaDBProperties">KahaDB Properties</h3><div
class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1"
rowspan="1" class="confluenceTh"><p>property name</p></th><th colspan="1"
rowspan="1" class="confluenceTh"><p>default value</p></th><th colspan="1"
rowspan="1" class="confluenceTh"><p>Comments</p></th></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>archiveCorruptedIndex</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>If enabled, corrupted indexes found
at startup will be archived (not deleted).</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>archiveDataLogs</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>If enabled, will move a message data
log to the archive directory instead of deleting it.</p></t
 d></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>checkForCorruptJournalFiles</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>If enabled, will check for corrupted
Journal files on startup and try and recover them.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>checkpointInterval</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>5000</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Time (ms) before check-pointing the
journal.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>checksumJournalFiles</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Create a checksum for a journal file
- to enable checking for corrupted journals.</p><p>Before <strong>ActiveMQ
5.9.0</strong>: the default i
 s <strong><code>false</code></strong>.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>cleanupInterval</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>30000</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Time (ms) before checking for a discarding/moving
message data logs that are no longer used.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>compactAcksAfterNoGC</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>10</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>From <strong>ActiveMQ 5.14.0</strong>:
when the acknowledgement compaction feature is enabled this value controls how many store
GC cycles must be completed with no other files being cleaned up before the compaction logic
is triggered to possibly compact older acknowledgements spread across journal files into a
new log file.&#160; The lower the value set the faster the compaction may oc
 cur which can impact performance if it runs to often.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>compactAcksIgnoresStoreGrowth</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>From <strong>ActiveMQ 5.14.0</strong>:&#160;when
the acknowledgement compaction feature is enabled this value controls whether compaction is
run when the store is still growing or if it should only occur when the store has stopped
growing (either due to idle or store limits reached).&#160; If enabled the compaction
runs regardless of the store still having room or being active which can decrease overall
performance but reclaim space faster.&#160;</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>concurrentStoreAndDispatchQueues</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td
colspan="1" rowspan="1" class="confl
 uenceTd"><p>Enable the dispatching of Queue messages to interested clients to happen
concurrently with message storage.</p></td></tr><tr><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>concurrentStoreAndDispatchTopics</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Enable the dispatching of Topic messages
to interested clients to happen concurrently with message storage</p><div class="confluence-information-macro
confluence-information-macro-warning"><span class="aui-icon aui-icon-small aui-iconfont-error
confluence-information-macro-icon"></span><div class="confluence-information-macro-body">Enabling
this property is not recommended.</div></div></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>directory</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>activemq-data</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p
 >The path to the directory to use to store the message store data and log files.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>directoryArchive</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>null</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Define the directory to move data
logs to when they all the messages they contain have been consumed.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>enableAckCompaction</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>From <strong>ActiveMQ 5.14.0</strong>:
this setting controls whether the store will perform periodic compaction of older journal
log files that contain only Message acknowledgements.&#160; By compacting these older
acknowledgements into new journal log files the older files can be removed freeing space and
allowing the message store to
  continue to operate without hitting store size limits.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>enableIndexWriteAsync</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>If set, will asynchronously write
indexes.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>enableJournalDiskSyncs</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Ensure every journal write is followed
by a disk sync (JMS durability requirement).</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>ignoreMissingJournalfiles</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>If enabled, will ignore a missing
message log file.</p></td></tr><tr><td colspan=
 "1" rowspan="1" class="confluenceTd"><p><code>indexCacheSize</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>10000</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Number of index pages cached in memory.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>indexDirectory</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd">&#160;</td><td colspan="1" rowspan="1"
class="confluenceTd"><p><span>From <strong>ActiveMQ 5.10.0</strong>:
If set, configures where the KahaDB index files (<strong><code>db.data</code></strong>
and&#160;<strong><code>db.redo</code></strong>) will be stored.
If not set, the index files are stored in the directory specified by the&#160;<strong><code>directory</code></strong>
attribute.</span></p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>indexWriteBatchSize</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>1000</code></p></td><td
colspan="
 1" rowspan="1" class="confluenceTd"><p>Number of indexes written in a batch.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>journalMaxFileLength</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>32mb</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>A hint to set the maximum size of
the message data logs.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>maxAsyncJobs</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>10000</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>The maximum number of asynchronous
messages that will be queued awaiting storage (should be the same as the number of concurrent
MessageProducers).</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>preallocationScope</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><code>entire_journal</code></td><td
colspan="1" rowspan="1" class="confluenceTd"><
 p>From <strong>ActiveMQ 5.14.0</strong>: this setting configures how journal
data files are preallocated. The default strategy preallocates the journal file on first use
using the appender thread.&#160;</p><ul><li><strong><code>entire_journal_async</code></strong>
will use preallocate ahead of time in a separate thread.</li><li><strong><code>none</code></strong>
disables preallocation.</li></ul><p>On SSD, using&#160;<strong><code>entire_journal_async</code></strong>
avoids delaying writes pending preallocation on first use.</p><p><strong>Note</strong>:
on HDD the additional thread contention for disk has a negative impact. Therefore use the
default.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>preallocationStrategy</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>sparse_file</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>From <strong>ActiveMQ 5.12.0</strong>:&#160;This
setting configures how the broker will tr
 y to preallocate the journal files when a new journal file is needed.</p><ul><li><strong><code>sparse_file</code></strong>
- sets the file length, but does not populate it with any data.</li><li><strong><code>os_kernel_copy</code></strong>
- delegates the preallocation to the Operating System.</li><li><strong><code>zeros</code></strong>&#160;
- each preallocated journal file contains nothing but <strong><code>0x00</code></strong>
throughout.</li></ul></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>storeOpenWireVersion</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>11</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Determines the version of OpenWire
commands that are marshaled to the KahaDB journal.&#160;</p><p>Before <strong>ActiveMQ
5.12.0</strong>: the default value is <strong><code>6</code></strong>.</p><p>Some
features of the broker depend on information stored in the OpenWire commands from newer protocol
revis
 ions and these may not work correctly if the store version is set to a lower value.&#160;
KahaDB stores from broker versions greater than 5.9.0 will in many cases still be readable
by the broker but will cause the broker to continue using the older store version meaning
newer features may not work as intended.&#160;</p><p>For KahaDB stores that
were created in versions prior to <strong>ActiveMQ 5.9.0</strong> it will be necessary
to manually set <strong><code>storeOpenWireVersion="6"</code></strong>
in order to start a broker without error.</p></td></tr></tbody></table></div><p>For
tuning locking properties please take a look at <a shape="rect" href="pluggable-storage-lockers.html">Pluggable
storage lockers</a></p><h3 id="KahaDB-Slowfilesystemaccessdiagnosticlogging">Slow
file system access diagnostic logging</h3><p>You can configure a non zero threshold
in milliseconds for database updates. If database operation is slower than that threshold
(for example if you set it to 500), you 
 may see messages like</p><div class="panel" style="border-width: 1px;"><div
class="panelContent">
+</div></div><h3 id="KahaDB-KahaDBProperties">KahaDB Properties</h3><div
class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1"
rowspan="1" class="confluenceTh"><p>property name</p></th><th colspan="1"
rowspan="1" class="confluenceTh"><p>default value</p></th><th colspan="1"
rowspan="1" class="confluenceTh"><p>Comments</p></th></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>archiveCorruptedIndex</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>If enabled, corrupted indexes found
at startup will be archived (not deleted).</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>archiveDataLogs</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>If enabled, will move a message data
log to the archive directory instead of deleting it.</p></t
 d></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>checkForCorruptJournalFiles</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>If enabled, will check for corrupted
Journal files on startup and try and recover them.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>checkpointInterval</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>5000</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Time (ms) before check-pointing the
journal.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>checksumJournalFiles</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Create a checksum for a journal file
- to enable checking for corrupted journals.</p><p>Before <strong>ActiveMQ
5.9.0</strong>: the default i
 s <strong><code>false</code></strong>.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>cleanupInterval</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>30000</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Time (ms) before checking for a discarding/moving
message data logs that are no longer used.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>compactAcksAfterNoGC</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>10</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>From <strong>ActiveMQ 5.14.0</strong>:
when the acknowledgement compaction feature is enabled this value controls how many store
GC cycles must be completed with no other files being cleaned up before the compaction logic
is triggered to possibly compact older acknowledgements spread across journal files into a
new log file.&#160; The lower the value set the faster the compaction may oc
 cur which can impact performance if it runs to often.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>compactAcksIgnoresStoreGrowth</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>From <strong>ActiveMQ 5.14.0</strong>:&#160;when
the acknowledgement compaction feature is enabled this value controls whether compaction is
run when the store is still growing or if it should only occur when the store has stopped
growing (either due to idle or store limits reached).&#160; If enabled the compaction
runs regardless of the store still having room or being active which can decrease overall
performance but reclaim space faster.&#160;</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>concurrentStoreAndDispatchQueues</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td
colspan="1" rowspan="1" class="confl
 uenceTd"><p>Enable the dispatching of Queue messages to interested clients to happen
concurrently with message storage.</p></td></tr><tr><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>concurrentStoreAndDispatchTopics</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Enable the dispatching of Topic messages
to interested clients to happen concurrently with message storage</p><div class="confluence-information-macro
confluence-information-macro-warning"><span class="aui-icon aui-icon-small aui-iconfont-error
confluence-information-macro-icon"></span><div class="confluence-information-macro-body">Enabling
this property is not recommended.</div></div></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>directory</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>activemq-data</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p
 >The path to the directory to use to store the message store data and log files.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>directoryArchive</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>null</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Define the directory to move data
logs to when they all the messages they contain have been consumed.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>enableAckCompaction</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>From <strong>ActiveMQ 5.14.0</strong>:
this setting controls whether the store will perform periodic compaction of older journal
log files that contain only Message acknowledgements.&#160; By compacting these older
acknowledgements into new journal log files the older files can be removed freeing space and
allowing the message store to
  continue to operate without hitting store size limits.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>enableIndexWriteAsync</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>If set, will asynchronously write
indexes.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>enableJournalDiskSyncs</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><span>Ensure every journal
write is followed by a disk sync (JMS durability requirement).</span></p><div
class="confluence-information-macro confluence-information-macro-warning"><span class="aui-icon
aui-icon-small aui-iconfont-error confluence-information-macro-icon"></span><div
class="confluence-information-macro-body">This property is deprecated as of ActiveMQ 5.14.0,
see <span style="color: rgb(34,34,34)
 ;">journalDiskSyncStrategy for version 5.14.0 and newer.</span></div></div></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><code><span>journalDiskSyncStrategy</span></code></td><td
colspan="1" rowspan="1" class="confluenceTd">always</td><td colspan="1" rowspan="1"
class="confluenceTd"><p>From <strong>ActiveMQ 5.14.0</strong>: this setting
configures the disk sync policy. The default strategy is set to <strong>always</strong>.</p><ul><li><strong><code>always</code></strong>
<span>Ensure every journal write is followed by a disk sync (JMS durability requirement).
This is the safest option but is also the slowest because it requires a sync after every message
write. This is equivalent to the deprecated property enableJournalDiskSyncs being set to true.</span></li><li><strong><code>periodic</code></strong>
<span style="color: rgb(34,34,34);">The disk will be synced at set intervals (if a write
has occurred) instead of after every journal write which will reduce the load o
 n the disk and should improve throughput</span>. The disk will also be synced when
rolling over to a new journal file. The default setting is set to 1 second which generally
provides very good performance while being safer than never disk syncing as only up to 1 second
of data can be lost. See <strong>journalDiskSyncInterval</strong> to change the
frequency of disk syncs.</li><li><strong><code>never</code></strong>
A sync will never be explicitly called and it will be up to the operating system to flush
to disk. This is equivalent to setting the deprectated enableJournalDiskSyncs property to
false. This is the fastest option but is the least safe as there's no guarantee as to when
data is flushed to disk so message loss can occur on failure.</li></ul></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><code><span>journalDiskSyncInterval</span></code></td><td
colspan="1" rowspan="1" class="confluenceTd">1000</td><td colspan="1" rowspan="1"
class="confluenceTd">Interval (ms
 ) for when to perform a disk sync when <strong>journalDiskSyncStrategy</strong>
is set to <strong>periodic</strong>. A sync will only be performed if a write
has occurred to the journal since the last disk sync or when the journal rolls over to a new
journal file.</td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>ignoreMissingJournalfiles</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>If enabled, will ignore a missing
message log file.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>indexCacheSize</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>10000</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Number of index pages cached in memory.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>indexDirectory</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd">&#160;<
 /td><td colspan="1" rowspan="1" class="confluenceTd"><p><span>From <strong>ActiveMQ
5.10.0</strong>: If set, configures where the KahaDB index files (<strong><code>db.data</code></strong>
and&#160;<strong><code>db.redo</code></strong>) will be stored.
If not set, the index files are stored in the directory specified by the&#160;<strong><code>directory</code></strong>
attribute.</span></p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>indexWriteBatchSize</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>1000</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Number of indexes written in a batch.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>journalMaxFileLength</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>32mb</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>A hint to set the maximum size of
the message data logs.</p></td></tr><tr><td colspan="1" 
 rowspan="1" class="confluenceTd"><p><code>maxAsyncJobs</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>10000</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>The maximum number of asynchronous
messages that will be queued awaiting storage (should be the same as the number of concurrent
MessageProducers).</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>preallocationScope</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><code>entire_journal</code></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>From <strong>ActiveMQ 5.14.0</strong>:
this setting configures how journal data files are preallocated. The default strategy preallocates
the journal file on first use using the appender thread.&#160;</p><ul><li><strong><code>entire_journal_async</code></strong>
will use preallocate ahead of time in a separate thread.</li><li><strong><code>none</code></strong>
disables preallocation.</li></ul><p>On SSD,
  using&#160;<strong><code>entire_journal_async</code></strong>
avoids delaying writes pending preallocation on first use.</p><p><strong>Note</strong>:
on HDD the additional thread contention for disk has a negative impact. Therefore use the
default.</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><code>preallocationStrategy</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>sparse_file</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>From <strong>ActiveMQ 5.12.0</strong>:&#160;This
setting configures how the broker will try to preallocate the journal files when a new journal
file is needed.</p><ul><li><strong><code>sparse_file</code></strong>
- sets the file length, but does not populate it with any data.</li><li><strong><code>os_kernel_copy</code></strong>
- delegates the preallocation to the Operating System.</li><li><strong><code>zeros</code></strong>&#160;
- each preallocated journal file contains nothing but <strong><
 code>0x00</code></strong> throughout.</li></ul></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>storeOpenWireVersion</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>11</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Determines the version of OpenWire
commands that are marshaled to the KahaDB journal.&#160;</p><p>Before <strong>ActiveMQ
5.12.0</strong>: the default value is <strong><code>6</code></strong>.</p><p>Some
features of the broker depend on information stored in the OpenWire commands from newer protocol
revisions and these may not work correctly if the store version is set to a lower value.&#160;
KahaDB stores from broker versions greater than 5.9.0 will in many cases still be readable
by the broker but will cause the broker to continue using the older store version meaning
newer features may not work as intended.&#160;</p><p>For KahaDB stores that
were created in versions prior to <strong>ActiveMQ 5.9.0</str
 ong> it will be necessary to manually set <strong><code>storeOpenWireVersion="6"</code></strong>
in order to start a broker without error.</p></td></tr></tbody></table></div><p>For
tuning locking properties please take a look at <a shape="rect" href="pluggable-storage-lockers.html">Pluggable
storage lockers</a></p><h3 id="KahaDB-Slowfilesystemaccessdiagnosticlogging">Slow
file system access diagnostic logging</h3><p>You can configure a non zero threshold
in milliseconds for database updates. If database operation is slower than that threshold
(for example if you set it to 500), you may see messages like</p><div class="panel"
style="border-width: 1px;"><div class="panelContent">
 <p><code>Slow KahaDB access: cleanup took 1277 | org.apache.activemq.store.kahadb.MessageDatabase
| ActiveMQ Journal Checkpoint Worker</code></p>
 </div></div><p>You can configure a threshold used to log these messages
by using a system property and adjust it to your disk speed so that you can easily pick up
runtime anomalies.</p><div class="panel" style="border-width: 1px;"><div class="panelContent">
 <p><code>-Dorg.apache.activemq.store.kahadb.LOG_SLOW_ACCESS_TIME=1500</code></p>



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