Is it possible to delete the actives while you are running a loop over an internal table in SAP ABAP?

The DELETE command will have a result. You should make sure that once you delete the row, there should not be any reference or use of that row subsequently in the loop. The best practice is to use CONTINUE as soon as you perform deletion.

Best Practices for Deleting Records

I suggest avoiding "DELETE lt_itab INDEX sy-tabix" because it will change the sy-tabix (table index) and can lead to unexpected behavior. When you delete a row, all subsequent rows shift up, making the index unreliable for the remainder of the loop.

If you want to delete the current row in the loop, you can simply use ?

DELETE lt_itab.

This approach deletes the current record being processed without affecting the loop's integrity.

Alternative Deletion Methods

If you are using the statement "DELETE lt_itab FROM ls_wa", then whether knowingly or unknowingly, you are deleting all matching lines from the internal table based on the work area content, not just the current row.

LOOP AT lt_itab INTO ls_wa.
  IF ls_wa-field = 'DELETE_CONDITION'.
    DELETE lt_itab.
    CONTINUE.
  ENDIF.
  " Process remaining records
ENDLOOP.

Conclusion

If you are updating or modifying the table over which you are currently running a loop, be very careful about what you are doing. Always use DELETE lt_itab instead of index-based deletion to maintain loop stability.