how to know structure of internal table used in ASSIGN statement..

hello all,

for a particular exit i am using the following statements,

field-symbols : <fs1> type any.

field-symbols : <fs2> type any.

ASSIGN ('(SAPLCJWB)L_PRPS') to <fs1>.

ASSIGN  ('(SAPLCJDW)*PRPS')  to <fs2>.

Issue1

----------

here how do i find the structure of L_PRPS and *PRPS.

Issue2

---------

similarly

for a particular transaction , while writing user exits

to get current data from transaction how do i know which assign like(ASSIGN ('(SAPLCJWB) )

statement do i need to use...

thanks in advance...