This is important, otherwise one can't save files or get email after a user is created.
Enter SYSMAN to check (for example) the SYSTEM user quota, or other users in the UIC 200
$ RUN SYS$SYSTEM:SYSMAN
SYSMAN> diskquota show [*,*] /device=$1$dia0:
For every new user there has to be a matching quota set, use others in the same UIC group to match.
Assume the user you want to add is UIC = 200,3 and in this group the other quotas are 2000...
SYSMAN> diskquota add [200,3] /device=$1$dia0: /permquota=2000 /overdraft=2000