JavaCard OS

I am programming an applet in JCIDE. In fact, I want to create a method to store transactions logs in java card and call it from my outside application. The problem is I don't know how to get started with this issue. Any pointers?

Just create a byte[] with the size that equals to the transactions size and then store data into that array by TLV and decode it using the TLV when receiving on host side.

If you only need to keep a certain number, use a circular file. When it fills it starts overwriting the oldest. If you have to keep them all then a record based file. It also depends on if they are the same length or varying lengths.