Questions about simulating sample data

[bigbigben]

1. How to generate different samples at each run?
If I set simul_seed to any integer, it gives me the same sample everytime. However, if I don't specify any, it still give me the same sample, how should I fix it?

2. If I specify more than one shocks in the shock block, do I get samples simulated by all the shocks or just one of them?

3. How should I save the simulated data to a m file or a mat file?

I followed the example RBC_GenData. However, the generated data contains a huge column for one variable, while the data is supposed to consist of serveral series. The command I use is datatomfile('simuldataRBC',[]) to save the simulated data. In the generated file, it only has one variable,y_t.

Thanks for your input.