ORA-12537: TNS:connection closed exception with ASP.NET

i am getting this weired error, I am using SQLDataSource. I am getting this error somertimes only.
ORA-12537: TNS:connection closed
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Data.OracleClient.OracleException: ORA-12537: TNS:connection closed


Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
 


Stack Trace:

 
[OracleException (0x80131938): ORA-12537: TNS:connection closed
]
   System.Data.OracleClient.OracleConnection.CheckError(OciErrorHandle errorHandle, Int32 rc) +190
   System.Data.OracleClient.OracleCommand.Execute(OciStatementHandle statementHandle, CommandBehavior behavior, Boolean needRowid, OciRowidDescriptor& rowidDescriptor, ArrayList& resultParameterOrdinals) +988
   System.Data.OracleClient.OracleCommand.Execute(OciStatementHandle statementHandle, CommandBehavior behavior, ArrayList& resultParameterOrdinals) +25
   System.Data.OracleClient.OracleCommand.ExecuteReader(CommandBehavior behavior) +138
   System.Data.OracleClient.OracleCommand.ExecuteDbDataReader(CommandBehavior behavior) +4
   System.Data.Common.DbCommand.System.Data.IDbCommand.ExecuteReader(CommandBehavior behavior) +10
   System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) +130
   System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) +287
   System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, String srcTable) +92
   System.Web.UI.WebControls.SqlDataSourceView.ExecuteSelect(DataSourceSelectArguments arguments) +1297
   System.Web.UI.DataSourceView.Select(DataSourceSelectArguments arguments, DataSourceViewSelectCallback callback) +19
   DevExpress.Web.ASPxClasses.Internal.DataHelper.PerformSelect() +149
   DevExpress.Web.ASPxGridView.GridViewDataHelper.PerformSelect() +119
   DevExpress.Web.ASPxClasses.Internal.DataContainer.PerformSelect() +112
   DevExpress.Web.ASPxClasses.ASPxDataWebControlBase.DataBindCore() +15
   DevExpress.Web.ASPxClasses.ASPxDataWebControlBase.DataBind() +104
   DevExpress.Web.ASPxGridView.ASPxGridView.DataBind() +248
   DevExpress.Web.ASPxClasses.Internal.DataHelperBase.EnsureDataBound(Boolean ensureChildControls) +89
   DevExpress.Web.ASPxClasses.Internal.DataContainer.EnsureDataBound() +120
   DevExpress.Web.ASPxClasses.ASPxDataWebControlBase.OnPreRender(EventArgs e) +22
   System.Web.UI.Control.PreRenderRecursiveInternal() +80
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Control.PreRenderRecursiveInternal() +171
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +842
 
Why it is failing sometimes only.