The following errors frequently occurrs. 
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05/16 00:00:00.001 INFO (SimpleThreadPoolWorker-5:) - Purging data with resolution=3 that is 1 day(s) older than Wed May 16 00:00:00 JST 2018 (period start less than or equal to 1526310000001) in batches of 100. 
05/16 00:00:00.006 ERROR (SimpleThreadPoolWorker-3:) - [general] -- org.hibernate.SessionException: Session was already closed 
at org.hibernate.internal.SessionImpl.close(SessionImpl.java:344) 
at com.thelevel.lrs.xmlsources.monetization.RemoveExpiredMonetizedPlanRequest.getLRSXML(RemoveExpiredMonetizedPlanRequest.java:80) 
at com.thelevel.lrs.AbstractLRSSource.getXML(AbstractLRSSource.java:97) 
at com.thelevel.cms.xmlsources.AbstractXMLSource.getXML(AbstractXMLSource.java:172) 
at com.thelevel.cms.site.PageRule.handleRequest(PageRule.java:237) 
at com.thelevel.cms.site.CMSSiteHandler.handleRequest(CMSSiteHandler.java:488) 
at com.thelevel.cms.scheduler.ScheduleJob.execute(ScheduleJob.java:45) 
at org.quartz.core.JobRunShell.run(JobRunShell.java:202) 
at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:525) 

05/16 00:00:00.006 INFO (SimpleThreadPoolWorker-4:) - [LRSWrapper general] -- connected to https://api.west-ntt.net:8443/portalman/1/apis using GET 
05/16 00:00:00.008 ERROR (SimpleThreadPoolWorker-5:) - [DataPurger general] -- Failed to purge data. See xtreme output for trace. 
05/16 00:00:00.011 DEBUG (SimpleThreadPoolWorker-10:) - [Email general] -- thePath=
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What does it mean?
Is there a way to solve it?

Release:
Component: APIPRD

This log message has no impact on functionality.
It was a development issue, but there is no impact to functionality.
The problem will be fixed in Portal v3.5 CR9.