Convert OracleParameter.Value to Int32

You can also try:

Oracle.DataAccess.Types.OracleDecimal d = (Oracle.DataAccess.Types.OracleDecimal)cmd.Parameters["successCount"].Value;

if( d.IsNull )
    existsCount = 0;
else
    existsCount = d.ToInt32( );

What about

existsCount = int.Parse(cmd.Parameters["successCount"].Value.ToString());