That's not the name of exit, it's the name of the exception. If you check the subroutine where the exception is thrown, the descrition is:
*----------------------------------------------------------------------*
* FORM MERGE_ALLKSSK_ALLAUSP
*----------------------------------------------------------------------*
* Merge allocation and valuation tables from user exit (L_*)
* with corresponding tables in standard program (G_*).
*----------------------------------------------------------------------*
If this was my system I would put a break-point inside the perform, and debug.
* take over user changes into allkssk, allausp
perform merge_allkssk_allausp
tables allkssk
lt_allkssk
allausp
lt_allausp.