To be faster, ALPHA stores internally a lot of BOS bank indices in the ALPHA commons. Therefore one should absolutely avoid any BOS garbage collection during the execution of ALPHA since the program would crash immediately.
If you need to book your own BOS banks: use the BOS routines NBANK, MBANK, WBANK. One should absolutely avoid the use of the ALEPHLIB routine AUBOS since it performs a BOS garbage collection if the space is too small in the BOS array. Of course, the use of the BOS routines BGARB or WGARB in ALPHA is absolutely forbidden.