Hey Vyom,Thanks for the help I sorted it out...Actually the memory was leaking due t non-closure of a prepared Statement but there are some GREAT Java lessons that I learnt which I thought I must share with you guys:
1) Whenever coding that requires DB connectivity do remember do double check that all your DBConnections,PreparedStatements,ResultSet are properly closed. 2) If passing an object to a method, make sure you assign the object=null once you are through with the method. It wont affect the original object as in Java objects are not passed by reference... I know it's a POI forum but I thought why not share some Java intricacies. 3) I came across a tool that detects memory leak and tells what all objects are present in memory. It can really help someone to optimize the code. It comes with BEA's Jrockit. Try it out. Its awesome. http://e-docs.bea.com/wljrockit/docs142/userguide/memleak.html <http://e-docs.bea.com/wljrockit/docs142/userguide/memleak.html> (I am not working for BEA ;-) ) 4) Another article of interest that I came up with is: setupSet-up: optimized Java JVM configuration Application Developer is written in JavaTM, which poses some configuration questions. The IBM (r) and Sun Java JVMs have default configurations suitable for a wide range of Java applications. Their initial heap size is 4 MB, with a maximum equal to half of all the physical memory on your machine. Therefore, because Java applications cannot grow past the maximum heap size, they do not automatically consume a lot of memory, and can increase in size without consuming all of your memory. If you use Application Developer to develop and test a large number of complex programs, you may need to adjust your maximum heap size. To get an estimate of the appropriate heap size: 1. Determine the size of your physical memory (for example, 640 MB). 2. Subtract the amount of memory used for your operating system (for example, 210 MB). 3. Subtract the amount of memory used for typical concurrent tasks (for example, if the machine is primarily used for Application Developer, subtract 100 MB). 4. Tip: The number of KB of memory used by your operating system and your active tasks is shown in the Windows Task Manager in the bottom right-hand window (in our example, it would say Mem Usage: 310,000 KB). The total memory remaining will help you determine the appropriate maximum heap size. In our example, it is 640 - 310 = 330 MB. Now the tradeoffs. If you make your maximum heap too small, you'll run out of memory when building large applications. If you make it too large (or run too many concurrent applications), then parts of Application Developer will continuously swap in and out, causing an apparent system "hang" when swapping back in. If you make your initial heap too small, you'll slow startup as memory is continuously grabbed in pieces. If you make the initial heap too large, you'll prevent unused memory from being available to other system tasks. Also, remember that the actual running Java program (Application Developer) requires memory in addition to its data heap. So consider a maximum heap of 2/3 of your available memory as calculated above, and an initial heap of about 2/3 of that maximum heap. (The maximum heap is the critical piece; the initial heap is just a startup optimization.) Also, for major applications, you might even chose to set your initial heap equal to the maximum heap (as is often recommended for server applications). In our example with 330MB of available memory, you could make your maximum heap 250 MB and your initial heap 150 MB. When Java objects are released, the memory is not freed until "garbage collection" takes place. When the heap is initially used up, garbage collection will walk through all old objects and finally free the memory for reuse, causing an apparent "hang" during this processing. It may be better to be aggressive in regular garbage collection rather than letting it build up and result in a long collection. The default minimum free starting collection is 30% and the default maximum free stopping collection is 60%, but we really don't have enough experience yet to recommend changing the defaults. You can customize the Application Developer configuration using parameters with the startup program (wsappdev.exe). For example: wsappdev.exe -data MyWorkspace -vmargs -Xmx250m -Xms150m -Xminf0.40 -Xmaxf0.60 4)Another code optimizations that one can do with POI is: POI Optimization - eliminating trailing empty rows from an HSSFSheet. While my spreadsheet has only 7 rows with data, POI creates over 65,000 rows in the HSSFSheet object. This leads to a large amount of essentially unused memory. In order to free that memory, the following code snippet from my version of the public HSSFWorkbook(POIFSFileSystem fs, boolean preserveNodes) method works from bottom towards the top of the sheet removing empty rows. The code in bold performs the optimization. HSSFSheet hsheet = new HSSFSheet(workbook, sheet); boolean stop = false; boolean nonBlankRowFound; short c; HSSFRow lastRow = null; HSSFCell cell = null; while (stop == false) { nonBlankRowFound = false; lastRow = hsheet.getRow(hsheet.getLastRowNum()); for (c = lastRow.getFirstCellNum(); c <= lastRow.getLastCellNum(); c++) { cell = lastRow.getCell(c); if (cell != null && lastRow.getCell(c).getCellType() != HSSFCell.CELL_TYPE_BLANK) { nonBlankRowFound = true; } } if (nonBlankRowFound == true) { stop = true; } else { hsheet.removeRow(lastRow); } } sheets.add(hsheet); I hope it will be of some help to you guys....... Warm Regards, Mili Aggarwal ---------------------------------------------------------------------------- -----------------------------DISCLAIMER------------------------------------- ---------------------------------------------------------------------------- -------- This message and any attachment contained here are information that is confidential, proprietary to HCL Technologies and its customers. Contents may be privileged or otherwise protected by law. The information is solely intended for the individual or the entity it is addressed to. If you are not the intended recipient of this message, you are not authorized to read, forward, print, retain, copy or disseminate this message or any part of it. If you have received this e-mail in error, please notify the sender immediately by return e-mail and delete it from your computer. -----Original Message----- From: Vyom Tewari [mailto:[EMAIL PROTECTED] Sent: Thursday, April 07, 2005 10:40 AM To: POI Users List Subject: Re: out of memory. hi Milli can u send ur code ,in ur last mail u told that, u explicitly assign null to the workbook object inside loop ,it means gc should recollect it and according to u it is not working so if possible send ur code. ----- Original Message ----- From: "Mili Aggarwal, Noida" <[EMAIL PROTECTED]> To: "POI Users List" <[email protected]> Sent: Thursday, April 07, 2005 9:58 AM Subject: out of memory. > He guys I have be unable to resolve out of memory error when I am creating > 300 odd workbooks. > The structure of my app is: > > Reportgenerater is the class that calls 2 classes((Sheet1 and Sheet2)) by > passing them workbook object to Create sheets. The 2 classes create one > sheet each. There is a common class that consists of all STATIC styles that > are applied to both the sheets. Now the problem is - I am running out memory > since the workbooks objects are not being destroyed. Any ideas as to what > can be done to destroy the objects? > > > Warm Regards, > Mili Aggarwal > HCL TECHNOLOGIES LTD. > Noida, India. > Tel: +91 (0120) 2516321/328 Extn: 1052 > Email: [EMAIL PROTECTED] > > -------------------------------------------------------------------------- -- > -----------------------------DISCLAIMER----------------------------------- -- > -------------------------------------------------------------------------- -- > -------- > > This message and any attachment contained here are information that is > confidential, proprietary to HCL Technologies and its customers. Contents > may be privileged or otherwise protected by law. The information is solely > intended for the individual or the entity it is addressed to. If you are not > the intended recipient of this message, you are not authorized to read, > forward, print, retain, copy or disseminate this message or any part of it. > If you have received this e-mail in error, please notify the sender > immediately by return e-mail and delete it from your computer. > > > > > > > Disclaimer: > > This message and any attachment(s) contained here are information that is > confidential,proprietary to HCL Technologies and its customers, privileged > or otherwise protected by law.The information is solely intended for the > individual or the entity it is addressed to. If you are not the intended > recipient of this message, you are not authorized to read, forward, > print,retain, copy or disseminate this message or any part of it. If you > have received this e-mail in error, please notify the sender immediately by > return e-mail and delete it from your computer. > > > --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] Mailing List: http://jakarta.apache.org/site/mail2.html#poi The Apache Jakarta Poi Project: http://jakarta.apache.org/poi/ Disclaimer: This message and any attachment(s) contained here are information that is confidential,proprietary to HCL Technologies and its customers, privileged or otherwise protected by law.The information is solely intended for the individual or the entity it is addressed to. If you are not the intended recipient of this message, you are not authorized to read, forward, print,retain, copy or disseminate this message or any part of it. If you have received this e-mail in error, please notify the sender immediately by return e-mail and delete it from your computer.
