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POHow to increase the speed for writing clob data to a file
 

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  1. POHow to increase the speed for writing clob data to a file
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    <p>We are extracting data from an oracle database to a file using C# oracleDataReader, we are using multiple threads and I found that reading data other than clob is very fast say say 4 min for 1 GB. But when data contains clob it is very very slow, even a 12 MB clob data is taking some 3 hours. </p> <p>I tried increasing the buffer from 64 KB to 5MB.</p> <p>Please suggest how to increase the speed to write clob to a file.</p> <p>Source code</p> <p>we are using 2 files 1 for actual csv and 1 for clob. we write recordpointer in place of clob in csv file and in clob file we write recordpointer, clob value. </p> <pre><code>else if (objVal is OracleClob) { OracleClob oraVal = (OracleClob)objVal; if (oraVal.IsEmpty) sw.Write(""); else { // using (StreamWriter writer = new StreamWriter(fileName, true)) { Interlocked.Increment(ref recordPointer); if (recordPointer == 1) { string fileName = outputFileName.Remove(outputFileName.LastIndexOf(".")); fileName = fileName + ".clobcsv"; clobWriter = new StreamWriter(fileName, true); log.Info("CLOB data is found in this file " + outputFileName + " and clob data is stored in " + fileName + " file"); clobWriter.WriteLine("Id," + cols[i]); } StringBuilder sb = new StringBuilder("\""); StringBuilder value = new StringBuilder(); value.Append(oraVal.Value); //CsvEscape(value.ToString()); value.Replace("\"", "\"\""); sb.Append(recordPointer); sb.Append("\""); sb.Append(delimiter); sb.Append("\""); //sb.Append(oraVal.Value.Replace("\"", "\"\"")); sb.Append(value); value.Clear(); sb.Append("\""); clobWriter.WriteLine(sb); //clobWriter.WriteLine("\"" + recordPointer + "\"" + delimiter + "\"" + oraVal.Value.Replace("\"", "\"\"") + "\""); } sw.Write(recordPointer); } } </code></pre>
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    1. USNaveen Chakravarthy
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    1. COYou say you're using multiple threads - have you checked to see if you're locking records while you read them? If you are waiting around for locked records, that would drastically decrease performance.
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    2. CO@RQDQ yes couple of places, but other data is loading very fast except clob.
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      1. USNaveen Chakravarthy
    3. CO@bunny - What does the code look like for reading / writing the CLOB?
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