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From Katherine Marsden <kmarsdende...@sbcglobal.net>
Subject Re: Quetion on out memory usage
Date Wed, 15 Feb 2012 17:09:55 GMT
On 2/15/2012 8:45 AM, Bergquist, Brett wrote:
>
> I had a user in our production server that performed a query through a 
> web service interface that requested to retrieve and perform a 
> multi-level sort on probably 30 million records.   The tables being 
> queried on are in a UNION (basically one table for each week of the 
> year and the query was working across the this week and the previous 
> week so it probably could not use the indexes to avoid the sort.
>
> Derby reported OutOfMemory errors.    In derby.log are errors such as:
>
> Tue Feb 14 20:15:12 EST 2012 Thread[DRDAConnThread_68,5,main] (XID = 
> 861337977), (SESSIONID = 45137761), (DATABASE = csemdb), (DRDAID = 
> ????????.??-866660124046835337{112060}), Failed Statement is: SELECT 
> r.MasterIp, BootCount, TestResultId, ProfileName, r.ProfileRefId, 
> LatencyBucketsInUse, JitterBucketsInUse, UseOutOfSequence, 
> StartDateTime, TestResultDescription, TestResultDescription2, 
> PacketsSent, RoundTripPackets, OutOfOrderPackets, MinRoundTripLatency, 
> MaxRoundTripLatency, TotalRoundTripLatency, LatencyBucketValue1, 
> LatencyBucketValue2, LatencyBucketValue3, LatencyBucketValue4, 
> LatencyBucketValue5, LatencyBucketValue6, LatencyBucketValue7, 
> LatencyBucketValue8, LatencyBucketValue9, LatencyBucketValue10, 
> JitterMeasurement, LocalRemoteJitterBucketValue1, 
> LocalRemoteJitterBucketValue2, LocalRemoteJitterBucketValue3, 
> LocalRemoteJitterBucketValue4, LocalRemoteJitterBucketValue5, 
> LocalRemoteJitterBucketValue6, LocalRemoteJitterBucketValue7, 
> LocalRemoteJitterBucketValue8, LocalRemoteJitterBucketValue9, 
> MinLocalRemoteJitter, MaxLocalRemoteJitter, TotalLocalRemoteJitter, 
> RemoteLocalJitterBucketValue1, RemoteLocalJitterBucketValue2, 
> RemoteLocalJitterBucketValue3, RemoteLocalJitterBucketValue4, 
> RemoteLocalJitterBucketValue5, RemoteLocalJitterBucketValue6, 
> RemoteLocalJitterBucketValue7, RemoteLocalJitterBucketValue8, 
> RemoteLocalJitterBucketValue9, MinRemoteLocalJitter, 
> MaxRemoteLocalJitter, TotalRemoteLocalJitter, c1.Circuit as Circuit1, 
> c2.Circuit as Circuit2 FROM PCS_V1.NPAResults r JOIN 
> PCS_V1.NpaResultsProfile p on r.PROFILEREFID = p.PROFILEREFID JOIN 
> PCS_V1.NPAResultsAddress a on r.ADDRESSREFID = a.ADDRESSREFID JOIN 
> PCS_V1.NPAResultsCircuit c1 on r.CIRCUIT1REFID = c1.CIRCUITREFID JOIN 
> PCS_V1.NPAResultsCircuit c2 on r.CIRCUIT2REFID = c2.CIRCUITREFID WHERE 
> ReportKey >= '2012-02-03 12:45:00.0' AND ReportKey <= '2012-02-14 
> 14:00:00.0'  AND (r.ResultFlag = 0 OR (r.ResultFlag <> 0 AND 
> r.RoundTripPackets > 0)) ORDER BY TestResultDescription, Circuit1, 
> TestResultDescription2, ProfileName, StartDateTime
>
> java.lang.OutOfMemoryError: GC overhead limit exceeded
>

I have not personally encountered the GC overhead limit, but google 
search indicates it is related to the amount of time spent on garbage 
collection ("too much") and can be overridden.
http://www.petefreitag.com/item/746.cfm

> Tue Feb 14 23:48:28 EST 2012 Thread[DRDAConnThread_122,5,main] (XID = 
> 861195891), (SESSIONID = 45103057), (DATABASE = csemdb), (DRDAID = 
> ????????.??-448669783631952048{111972}), Failed Statement is: SELECT 
> r.MasterIp, BootCount, TestResultId, ProfileName, r.ProfileRefId, 
> LatencyBucketsInUse, JitterBucketsInUse, UseOutOfSequence, 
> StartDateTime, TestResultDescription, TestResultDescription2, 
> PacketsSent, RoundTripPackets, OutOfOrderPackets, MinRoundTripLatency, 
> MaxRoundTripLatency, TotalRoundTripLatency, LatencyBucketValue1, 
> LatencyBucketValue2, LatencyBucketValue3, LatencyBucketValue4, 
> LatencyBucketValue5, LatencyBucketValue6, LatencyBucketValue7, 
> LatencyBucketValue8, LatencyBucketValue9, LatencyBucketValue10, 
> JitterMeasurement, LocalRemoteJitterBucketValue1, 
> LocalRemoteJitterBucketValue2, LocalRemoteJitterBucketValue3, 
> LocalRemoteJitterBucketValue4, LocalRemoteJitterBucketValue5, 
> LocalRemoteJitterBucketValue6, LocalRemoteJitterBucketValue7, 
> LocalRemoteJitterBucketValue8, LocalRemoteJitterBucketValue9, 
> MinLocalRemoteJitter, MaxLocalRemoteJitter, TotalLocalRemoteJitter, 
> RemoteLocalJitterBucketValue1, RemoteLocalJitterBucketValue2, 
> RemoteLocalJitterBucketValue3, RemoteLocalJitterBucketValue4, 
> RemoteLocalJitterBucketValue5, RemoteLocalJitterBucketValue6, 
> RemoteLocalJitterBucketValue7, RemoteLocalJitterBucketValue8, 
> RemoteLocalJitterBucketValue9, MinRemoteLocalJitter, 
> MaxRemoteLocalJitter, TotalRemoteLocalJitter, c1.Circuit as Circuit1, 
> c2.Circuit as Circuit2 FROM PCS_V1.NPAResults r JOIN 
> PCS_V1.NpaResultsProfile p on r.PROFILEREFID = p.PROFILEREFID JOIN 
> PCS_V1.NPAResultsAddress a on r.ADDRESSREFID = a.ADDRESSREFID JOIN 
> PCS_V1.NPAResultsCircuit c1 on r.CIRCUIT1REFID = c1.CIRCUITREFID JOIN 
> PCS_V1.NPAResultsCircuit c2 on r.CIRCUIT2REFID = c2.CIRCUITREFID WHERE 
> ReportKey >= '2012-02-03 12:45:00.0' AND ReportKey <= '2012-02-14 
> 14:00:00.0'  AND (r.ResultFlag = 0 OR (r.ResultFlag <> 0 AND 
> r.RoundTripPackets > 0)) ORDER BY TestResultDescription, Circuit1, 
> TestResultDescription2, ProfileName, StartDateTime
>
> java.lang.OutOfMemoryError: Java heap space
>
> The server is a Oracle M3000 and the Derby engine heap is setup to be 
> 8Gb.
>
For a heap out of memory, I have seen occasional cases where  Derby's 
estimate of whether it can sort in memory is wrong.   You'd need to look 
at the plan and do some debugging with the actual query  if you are able 
to reproduce to find out if that is the case here.


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