SCPI: Decimation factor and time scale does not work (python)

[s6ubkikran]

I'm using the given Example of the redpitaya documentation under "2.3.1.4.4.1. On trigger signal acquisition". Additionally to the given code, I'd like to change the decimation factor and hence the sampling rate. If I change it as stated in the doc, "rp.tx_txt('ACQ:DEC 8')", where rp is a redpitaya_scpi object from the given scpi-communication python script, the value does change, since when I read the value of the decimation the given value is returned. Yet, the acquired data doesn't change or better the timescale does not change (I receive a simple sine signal, which is verified with the internal oscilloscope). Do I have to change any other value as well?
How could I get a larger sampling rate, if this method does not work?

Thank You