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. 
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>: 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).  If enabled the compaction runs regardless
of the store still having room or being active which can decrease overall
performance but reclaim space faster. </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.  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"> </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 <strong><code>db.redo</code></strong>) will be stored. If not set, the
index files are stored in the directory specified by
the <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. </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 <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>: 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>  - 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. </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.  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. </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. 
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>: 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).  If enabled the compaction runs regardless
of the store still having room or being active which can decrease overall
performance but reclaim space faster. </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.  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"> <
/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 <strong><code>db.redo</code></strong>) will be stored. If not set, the
index files are stored in the directory specified by
the <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. </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 <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>: 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>  - 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. </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.  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. </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>
