OutOfMemory just in Mysql, not in Oracle or SqlServer

Hi everyone, i developing an application that downloads information of different databases and create plain text with that information.

Each 200,000 records, i going to the text plain and write the contents of a StringBuffer, and create a new one to continue record information in it.

In Oracle, my code work fine, with a table of 5,600,000 records, but in mysql, i get java.lang.OutOfMemoryError, even with much less records than in oracle.

My query in mysql is SELECT * FROM afiliados limit 500000, i try to record in the file each 50,000 records, but the results are the same.

My code is the following :

public void escribirTxt(String nomArchivo, TipoRegistroBean trb, ResultSet rs, String separador, BufferedWriter fw){
try {
CampoBean temp;
campos = trb.getCampos();
int numCampos = campos.size();
 
StringBuffer sb = new StringBuffer();

int cont = 1;

while(rs.next()){
//recorremos todos los campos sobre la misma fila del result set
int tamescrito = 0;
int posRecorrida =0;
for(int i=0; i<numCampos; i++){
temp = (CampoBean)campos.get(i);
nomDb = temp.getNombredb();
int tamanio = Integer.parseInt(temp.getHasta())-Integer.parseInt(temp.getDesde());
variable = alinear(rs.getString(temp.getNombredb()),temp.getCaracterrelleno(),temp.getAlineacion(),
tamanio, separador,Integer.parseInt(temp.getDesde()),tamescrito, temp.getValordefecto());
tamescrito += variable.length();
sb.append(variable);
}
//archivo = archivo + "\n";
sb.append("\n");

if(cont%50000==0){
escribirArchivo(sb.toString(),nomArchivo, fw);
sb = new StringBuffer();
}
cont++;

}
escribirArchivo(sb.toString(),nomArchivo, fw);

} catch (Exception e) {

e.printStackTrace();
}
}

Please help me in this situation,

Thanks and Regards,

[edited to add code tags]
[ March 05, 2005: Message edited by: Jeanne Boyarsky ]

Luis,
Do you know where the out of memory error is coming from? Maybe the driver?