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https://issues.apache.org/jira/browse/JENA-902?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14371226#comment-14371226
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Jan De Beer commented on JENA-902:
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Andy, I meant "exposed" more as in user documentation rather than API exposure
(although that is also relevant, of course). I'm actually fine with the tdb
properties file, but new users may not be aware of this feature. So, I favour
the suggestion of Bruno to document it in, say, one of the TDB pages on the
website.
> Default cache sizes too large / configurability should be more exposed
> ----------------------------------------------------------------------
>
> Key: JENA-902
> URL: https://issues.apache.org/jira/browse/JENA-902
> Project: Apache Jena
> Issue Type: Improvement
> Components: TDB
> Affects Versions: TDB 1.1.0
> Reporter: Jan De Beer
>
> In the class "com.hp.hpl.jena.tdb.sys.SystemTDB" there are two important
> cache size settings, namely "Node2NodeIdCacheSize" and
> "NodeId2NodeCacheSize". On a 64-bit platform, they default to 100000 and
> 500000 entries.
> In our setup of 5 TDB-backed graphs inside a single dataset, these default
> settings led to out-of-memory errors of the Fuseki server although setting
> the available heap memory to 3GB. It took some heap analysis to reveal that
> these two caches were the main memory consumers. Also, from the public
> documentation of Fuseki / TDB, it wasn't so obvious that their sizes can be
> configured. Only by looking into the source code, we found that one can use a
> TDB properties file to override the defaults.
> Proposed is to lower the default settings and have a more exposed
> documentation as to tuning the memory settings of TDB.
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