websphere6.1报outOfMemory，程序有的能运行有的出错
请教一个问题，最近websphere6.1每隔几天就会报outOfMemory(SystemErr.log文件里看到的)，但是应用没有宕掉，也没有生成javacore和heapdump文件。outOfMemory时访问应用程序有的功能能正常运行，有的就出错。操作系统是AIX，websphere版本是6.1.0.0，没有打过补丁.
在server1_exception.log里看到的错误日志如下：
Index Count Time of last Occurrence Exception SourceId ProbeId
------+------+---------------------------+--------------------------
1 6 11/3/11 8:49:21:269 CST javax.servlet.ServletException com.ibm.ws.webcontainer.filter.FilterInstanceWrapper.doFilter 144
2 44 11/3/11 8:50:06:444 CST java.lang.OutOfMemoryError com.ibm.ws.webcontainer.webapp.WebAppRequestDispatcher.forward 328
3 3 11/2/11 9:22:02:688 CST java.lang.ClassNotFoundException com.ibm.ws.webcontainer.webapp.WebAppServletManager.loadServlet 208
4 6550 11/3/11 8:49:54:193 CST java.io.FileNotFoundException com.ibm.ws.webcontainer.extension.DefaultExtensionProcessor.handleRequest 573
5 6 11/3/11 8:49:21:269 CST javax.servlet.ServletException com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest() 309
6 6 11/3/11 8:49:21:269 CST java.lang.OutOfMemoryError com.ibm.ws.webcontainer.servlet.ServletInstance.service 290
7 1 11/2/11 20:17:10:069 CST java.sql.SQLException com.ibm.ws.rsadapter.jdbc.WSJdbcStatement.pmiExecuteUpdate 1384
8 9 11/3/11 8:47:28:623 CST java.sql.SQLException com.ibm.ws.rsadapter.jdbc.WSJdbcStatement.pmiExecuteQuery 1315
9 103 11/3/11 8:47:13:815 CST com.ibm.wsspi.webcontainer.ClosedConnectionException com.ibm.ws.webcontainer.srt.BufferedWriter.writeOut 416
10 67 11/3/11 8:49:44:769 CST javax.servlet.ServletException com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter 82
11 9 11/3/11 8:47:28:623 CST java.sql.SQLException com.ibm.ws.rsadapter.jdbc.WSJdbcStatement.executeQuery 459
12 1 11/2/11 20:17:10:136 CST java.sql.SQLException com.ibm.ws.rsadapter.jdbc.WSJdbcStatement.executeUpdate 522
------+------+---------------------------+--------------------------
补充：企业软件 , WebSphere
