I think you want to allocate the dataset in TSO environment! So please refer the following sample -
"ALLOC F(LOGICAL) DA('[i]<Dataset Name>[/i]') NEW DIR(10)
SPACE(10,10)DSORG(PO) RECFM(F,B) LRECL(80) BLKSIZE(800)"
Byu this you will be able to allocate a dataset. Here it is PO i.e it is a PDS. If you want to allocate a PS, change the DSORG from PO to PS and don't give the DIR() parameter.