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From dyozie <...@git.apache.org>
Subject [GitHub] incubator-hawq-docs pull request #69: HAWQ-1192 - add discussion of heap and...
Date Fri, 09 Dec 2016 00:00:17 GMT
Github user dyozie commented on a diff in the pull request:

    https://github.com/apache/incubator-hawq-docs/pull/69#discussion_r91634985
  
    --- Diff: pxf/TroubleshootingPXF.html.md.erb ---
    @@ -200,4 +200,107 @@ Examine/collect the log messages from `stdout`.
     
     ``` sql
     gpadmin=# SET client_min_messages=NOTICE
    -```
    \ No newline at end of file
    +```
    +
    +
    +## <a id="pxf-memcfg"></a>Mitigating PXF Memory Issues
    +
    +The Java heap size can be a limiting factor in PXF’s ability to serve many concurrent
requests or to run queries against large tables.
    +
    +You may run into situations where a query will hang or fail with an Out of Memory exception
(OOM). This typically occurs when many threads are reading different data fragments from an
external table and insufficient heap space exists to open all fragments at the same time.
To avert or remedy this situation, Pivotal recommends either increasing the Java maximum heap
size or decreasing the Tomcat maximum number of threads.
    +
    --- End diff --
    
    There should be some mention of why to modify one vs the other.  Is it simply a question
of, if you have enough memory you should increase heap size, and only reduce threads if you're
out of memory?


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