Thanks for the reply,
from log file.
processing!ReportServer_0-440!1b14!07/22/2015-08:25:29:: e ERROR: An exception has occurred in data set 'DataSet1'. Details: Microsoft.ReportingServices.ReportProcessing.ReportProcessingException: Query execution failed for dataset 'DataSet1'. ---> System.Data.SqlClient.SqlException:
Login failed for user 'reporting'.
Cannot open user default database. Login failed.
at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection)
at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj)
at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)
at System.Data.SqlClient.SqlDataReader.ConsumeMetaData()
at System.Data.SqlClient.SqlDataReader.get_MetaData()
at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString)
at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async)
at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result)
at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)
at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)
at System.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior)
at System.Data.Common.DbCommand.System.Data.IDbCommand.ExecuteReader(CommandBehavior behavior)
at Microsoft.ReportingServices.DataExtensions.SqlCommandWrapperExtension.ExecuteReader(CommandBehavior behavior)
at Microsoft.ReportingServices.OnDemandProcessing.RuntimeDataSet.RunEmbeddedQuery(Boolean& readerExtensionsSupported, Boolean& readerFieldProperties, List`1 queryParams, Object[] paramValues)