Camunda Tables, act_hi_varinst & act_ge_bytearray

I have a question about Camunda tables. Namely, act_hi_varinst & act_ge_bytearray.

The two tables store different parameters for each activity.

Do the entries in the table are also updated? Or are the entries only written after the activity is closed and can therefore no longer be changed? Basically a little longer explanation about the two.

Thanks in advance