Data not getting saved using RMS

In my j2me app, I write data using this:

RecordStore rs = RecordStore.openRecordStore("mydb", true);
String buf = "Some text";
rs.addRecord(buf.getBytes(), 0, buf.getBytes().length);
rs.closeRecordStore();

The data stays as long as the app is running, but when I restart the app, there is no "mydb"

I tested it on 开发者_JS百科emulator and device both. I know there can be some problems in emulator but it should work on the device at least.

I'm using: Java Me SDK 3.0 CLDC 1.1 MIDP 2.0 Device: Samsung S5620 OS:Vista

Is it related to some permissions or the app should be signed before running?