AMORTIS/i — Loan Origination & Servicing

Not to be confused with LOANSVC/i. A separate SteelFrame X application, LOANSVC/i (Consumer Loan Servicing), is documented elsewhere; it is an SQL-PL-driven consumer-instalment servicer. AMORTIS/i is a different application — its own library (AMORTIS), its own file/program set, and its own design: constant-principal term loans with the logic in RPG/COBOL programs rather than DB2 SQL PL.

A. Overview & Architecture ↑ top

A.1 What it does

AMORTIS/i services the full life of a term loan, in library AMORTIS:

• Origination (LNORIG). Take a PENDING loan, generate its complete constant-principal amortisation schedule (one LNSCHD row per instalment), then activate the loan — set the balance to the advance, status A, first due date.
• Daily interest accrual (LNACCRU). Accrue one day of interest on every active loan on a 30/360 basis, write an audit row per loan per day (LNACRD) and a ledger transaction (LNTXN type I), and add to the loan's unbilled accrual bucket.
• Payment application (LNCASH). Apply every unapplied receipt on a strict fees→interest→principal waterfall, with any surplus a principal prepayment.
• Delinquency re-bucketing (LNDELQP). Age each active loan by days-past-due of its oldest billed-unpaid instalment into buckets 0–4 and log movement to LNDELQ.
• Monthly billing & fees (LNBILLP, LNFEEPG). Bill every instalment falling due (in due-date order), relieve the accrual bucket by the interest billed, then charge servicing fees and escrow.
• GL posting (LNGLPST). Sum the ledger by type and write balanced DR/CR pairs into the SQL distribution table LNGLDIST.
• Weekly collections & payoff (LNARRWL, LNARRPR, LNQUOTE). Build and print the arrears worklist off the delinquency access path, and price an early-settlement payoff quotation per loan.
• Annual review & closure (LNYRSTM, LNRATRV, LNCLOSE). Report year-end interest, re-price the book against credit score, and close fully-repaid loans with an escrow refund.
• Inquiry (LNMENU, LNLOANIQ, LNSCHDIQ, LNPORTF). Online loan-position and amortisation-schedule screens, plus a COBOL portfolio-position report.

A.2 The amortisation model: constant-principal, exact to the cent

Every loan in AMORTIS is a constant-principal (straight-line) term loan, not a level-annuity loan — a deliberate modelling choice. The principal component of every instalment is fixed (original principal / term), the interest component declines with the balance, and the instalment therefore declines too:

  principal component  = original principal / term          (fixed)
  interest component_n = opening balance_n * periodic rate  (declining)
  instalment_n         = principal + interest_n             (declining)
  closing_n            = opening_n - principal              (declining)

The canonical loan LN000001 is 12,000.00 at 12.0000% over 12 monthly instalments. Periodic rate = 12.0000 / 12 / 100 = 0.010000; principal per instalment = 12000 / 12 = 1000.00.

  n=1  open 12000.00  int 120.00  prin 1000.00  inst 1120.00  close 11000.00
  n=2  open 11000.00  int 110.00  prin 1000.00  inst 1110.00  close 10000.00
  ...
  n=12 open  1000.00  int  10.00  prin 1000.00  inst 1010.00  close     0.00
  total interest = 0.01 * 1000 * (12+11+...+1) = 0.01 * 1000 * 78 = 780.00

When the advance does not divide evenly by the term, the schedule would never reach zero (30,000.00 over 36 left 0.12 outstanding), so the final instalment repays whatever is actually left — a real amortisation plug. The daily accrual uses the same 30/360 convention, so a full 30-day month accrues exactly the schedule's interest: a day on 12,000.00 at 12% is 12000 × 0.01 / 30 = 4.00, and 30 days is 120.00 — the interest the monthly billing bills. That 30/360 identity between accrual and schedule is the design's central invariant.

A.3 Component & flow

  ORIGINATION           ONLINE                    BATCH (the four CL cycles)
  -----------           ------                    -------------------------
  LNREFLD (seed)        LNMENU (5250 menu)        LNDAILY  -> LNACCRU  accrual
  LNORIG   builds         opt 1 -> LNLOANIQ                  LNCASH    payments
    LNSCHD schedule        opt 2 -> LNSCHDIQ                 LNDELQP   re-bucket
    activates loan                (subfile)       LNWEEK   -> LNARRWL  worklist
                                                            LNQUOTE   payoff quote
                        LNPORTF (COBOL report)              LNARRPR   print worklist
                                                  LNMONTH  -> LNBILLP  billing
     LNRUNDT (*DTAARA: accrual / cut-off /                  LNFEEPG   fees+escrow
      as-at run date, set by CHGDTAARA) --------.          LNGLPST   GL distribution
            |                                    |          LNPORTF   portfolio
            v                                    v LNYEAR  -> LNYRSTM  interest stmt
     LNLOAN  <--writes--- every posting program            LNRATRV   rate review
       |  \                                                LNCLOSE   matured closure
       |   +--> LNTXN   (durable ledger: I/B/C/F/S/X, one stable key per event)
       |   +--> LNACRD  (daily accrual detail, keyed LOANNO+ACDT)
       |   +--> LNDELQ  (delinquency movement history)
       +------> LNQUOT (payoff quotations)   LNGLDIST (SQL GL)   LNSCHD (schedule)

A single processing event (say, daily accrual) flows: operator sets the run date on the LNRUNDT data area → the LNDAILY CL cycle CALLs LNACCRU → it reads each active loan, computes the day's interest, writes an LNACRD detail row and an LNTXN ledger row (each guarded by a stable idempotency key), and advances the loan's LNACCR bucket.

A.4 Object inventory

Object	Type	Role
LNBRW	PF	Borrower master.
LNLOAN	PF	Loan master — the servicing spine.
LNSCHD	PF	Amortisation schedule (composite key LOANNO+SCHINS).
LNSCHDL	LF	Schedule keyed by due date (billing access path).
LNLOANL	LF	Loans keyed by bucket, omitting bucket 0 (collections path).
LNPAY	PF	Payment receipts as banked.
LNTXN	PF	Durable loan transaction ledger.
LNACRD	PF	Daily interest-accrual detail.
LNDELQ	PF	Delinquency-movement history.
LNQUOT	PF	Payoff / early-settlement quotations.
LNFEE	PF	Fee & escrow catalogue.
LNGLDIST	SQL table	Interest-income GL distribution (+index LNGLDACC).
LNLOAND / LNSCHDD / LNMENUD	DSPF	Inquiry, subfile-schedule, and menu display files.
LNARRP	PRTF	Arrears / collections worklist printer file.
LNREFLD / LNORIG	RPGLE	Reference-data seed / origination.
LNACCRU / LNCASH / LNDELQP	RPGLE	Daily-cycle programs.
LNBILLP / LNFEEPG / LNGLPST	RPGLE / SQLRPGLE	Monthly-cycle programs.
LNQUOTE / LNARRWL / LNARRPR	RPGLE	Weekly-cycle programs.
LNRATRV / LNCLOSE / LNYRSTM	RPGLE	Annual-cycle programs.
LNLOANIQ / LNSCHDIQ / LNMENU	RPGLE	Interactive inquiry programs.
LNPORTF	CBLLE	COBOL portfolio-position report.
LNSETUP	CLP	Create/compile every object.
LNDAILY / LNWEEK / LNMONTH / LNYEAR	CLP	The four job cycles.
LNRUNDT	*DTAARA	Run-date control (CHAR(10)) read by every dated batch program.

The full catalogue is 11 physical/logical DDS files + 1 SQL table (+index), 4 display/printer files, 17 RPG programs, 1 COBOL program and 5 CL programs, plus the LNRUNDT data area. Sections D and F expand each.

B. Online Transactions & Screens ↑ top

B.1 The command/entry line

AMORTIS/i has no CICS transaction identifiers and no menu-driven transid switch. On IBM i, each program is reached by name from a 5250 command-entry line (or via CL/JOBQ for the batch cycles). The operator equivalent of "type a transid and Enter" is "type a CALL command and Enter". Before invoking anything, the job's library list must include AMORTIS; every CL cycle does its own ADDLIBLE LIB(AMORTIS) first.

To do this	Type on the command line
Build/rebuild the whole application (once)	CALL AMORTIS/LNSETUP then CALL AMORTIS/LNREFLD
Originate the pending loans	CALL AMORTIS/LNORIG
Open the online menu	CALL AMORTIS/LNMENU
Open loan inquiry directly	CALL AMORTIS/LNLOANIQ
Open the amortisation-schedule subfile directly	CALL AMORTIS/LNSCHDIQ
Set the batch run date (before a dated cycle)	CHGDTAARA DTAARA(AMORTIS/LNRUNDT) VALUE(' YYYYMMDD')
Run a cycle	CALL AMORTIS/LNDAILY (or LNWEEK / LNMONTH / LNYEAR; or SBMJOB it)

The batch cycles take no CALL parameters; the dated programs read their processing date from the LNRUNDT data area (section F.3), so a scheduled submission is a bare CALL. Only LNMENU / LNLOANIQ / LNSCHDIQ are interactive; the batch programs run to completion and DSPLY a one-line result apiece.

B.2 The menu & inquiry screens

Main menu (LNMENU / LNMENUD)

A plain option menu. Key 1 for Loan Inquiry (CALLs LNLOANIQ) or 2 for the Amortisation Schedule (CALLs LNSCHDIQ); any other non-blank option shows Invalid option. F3 exits.

Loan inquiry (LNLOANIQ / LNLOAND)

A plain (non-subfile) screen. Key a loan number and Enter; the program CHAINs LNLOAN, looks the borrower name up in LNBRW, and shows the servicing position plus the derived payoff total — computed on the screen with the same formula LNQUOTE prices with (balance + accrued + billed-unpaid-interest + fees - escrow).

Amortisation schedule (LNSCHDIQ / LNSCHDD)

The application's natural subfile screen (record SSFL under control record SCTL, SFLPAG(6), SFLSIZ(60)). Key a loan number and Enter: the subfile is cleared and re-loaded with that loan's instalments before it is displayed, so each enquiry shows the schedule just keyed rather than the previous one. A 12-instalment schedule fills two pages, so Roll Up/Roll Down paging is genuinely exercised. The header shows the advance and the total interest over the life, summed from the schedule rows themselves (780.00 for LN000001).

B.3 Controls & audit workflow (no four-eyes maker–checker)

Honest statement: AMORTIS/i does not model a true four-eyes maker–checker / separate-authorization workflow. There is no "one user posts, a second user approves" step: a receipt in LNPAY is applied by LNCASH when the daily cycle runs, and origination through LNORIG builds-and-activates in one pass. The control model the application does have:

• Durable transaction ledger (LNTXN). Every money movement is journaled with a memo, the amount, its interest/principal split, and a post-transaction balance snapshot: accrual (I), billing (B), cash (C), fee/escrow (F), settlement (S), closure (X). The whole book is reconstructable from it.
• Accrual & delinquency detail (LNACRD, LNDELQ). Interest is auditable day by day, and every movement between delinquency buckets writes a history row — the collections desk sees direction of travel, not just current position.
• Status gating. Business state gates what can happen: LNORIG only schedules a loan in P; accrual, billing, fees, quoting and repricing act only on A loans; LNCLOSE settles only a zero-balance A loan and skips one already S.
• Separation of duties in the code. Cash application drives the balance to zero but does not settle the loan; refunding the escrow and flipping status to S belongs to LNCLOSE alone. (The source records that when both programs claimed settlement, the escrow was never refunded — a real bug, now fixed by that split.)
• Idempotency guards. Every posting program derives a stable ledger/detail key from a business key and refuses to double-post via CHAIN(EN) (section F.2). This is the integrity backbone in place of a DB-trigger layer.

In sum, the control posture is durable ledger + accrual/delinquency detail + status gating + key-based idempotency, all enforced in the programs, rather than a segregation-of-duties approval workflow.

C. Batch Jobs & the Periodic Cycle ↑ top

AMORTIS/i's servicing runs as four periodic CL cycles rather than one monolithic nightly job: a daily cycle (accrual + cash + re-bucket), a weekly cycle (worklist + payoff quotes), a monthly cycle (billing + fees + GL + portfolio), and an annual cycle (statement + rate review + closure). Each CL program does its own ADDLIBLE LIB(AMORTIS), CALLs its member programs in order, and sends a completion message. The dated programs take no parameters; each reads its processing date from the single LNRUNDT data area — so a scheduled/JOBQ submission sets the date, then simply calls the cycle.

-- set the processing date the next dated cycle runs for (CHAR(10), right-justified)
CHGDTAARA DTAARA(AMORTIS/LNRUNDT) VALUE('  20260116')

-- then submit the (parameterless) cycle
SBMJOB CMD(CALL PGM(AMORTIS/LNDAILY)) JOB(LNDAILY)

-- blank the data area to fall back to each program's built-in default date
CHGDTAARA DTAARA(AMORTIS/LNRUNDT) VALUE('          ')

C.1 Full batch program set

Program	Cycle	Purpose	Reads / writes	DSPLY result
LNREFLD	setup	Seed borrowers, fee catalogue, pending loans.	writes LNBRW/LNFEE/LNLOAN	LNREFLD BORROWERS=4 FEES=3 LOANS=4
LNORIG	setup	Build each pending loan's schedule, activate it.	writes LNSCHD; updates LNLOAN	LNORIG ORIGINATED=n SKIP=n
LNACCRU	daily	Accrue one day's 30/360 interest per active loan.	LNRUNDT; LNLOAN/LNACRD/LNTXN(I)	LNACCRU ACCRUED=n SKIP=n TOT=x
LNCASH	daily	Apply unapplied receipts on the waterfall.	LNPAY/LNLOAN/LNTXN(C)	LNCASH APPLIED=n SKIP=n
LNDELQP	daily	Age loans into buckets 0–4; log movement.	LNRUNDT; LNSCHD/LNLOAN/LNDELQ	LNDELQP CHECKED=n MOVED=n
LNARRWL	weekly	Total arrears by bucket for the collections desk.	LNLOANL/LNBRW	LNARRWL DELQ=n B1..B4=x TOT=x
LNQUOTE	weekly	Price a payoff quotation per active loan.	LNRUNDT; LNLOAN/LNQUOT	LNQUOTE QUOTED=n SKIP=n
LNARRPR	weekly	Print the arrears worklist (PRTF, page overflow).	LNLOANL/LNBRW → LNARRP	LNARRPR LINES=n TOT=x
LNBILLP	monthly	Bill instalments due (due-date order); relieve accrual.	LNRUNDT; LNSCHDL/LNLOAN/LNTXN(B)	LNBILLP BILLED=n SKIP=n TOT=x
LNFEEPG	monthly	Charge servicing fees & escrow on billed loans.	LNRUNDT; LNFEE/LNLOAN/LNTXN(F)	LNFEEPG CHARGED=n SKIP=n SVC=x ESC=x
LNGLPST	monthly	Sum ledger by type; write balanced DR/CR pairs.	LNTXN → LNGLDIST (SQL)	LNGLPST BATCH=202602 ROWS=n
LNYRSTM	annual	Total year-end interest / accrual / fees from ledger.	LNTXN/LNLOAN	LNYRSTM BILLED=n INT=x ACCR=x FEE=x
LNRATRV	annual	Re-price active loans against credit score (anchored).	LNLOAN/LNBRW/LNSCHD	LNRATRV CHECKED=n REPRICED=n
LNCLOSE	annual	Close zero-balance loans; refund escrow.	LNLOAN/LNTXN(X)	LNCLOSE CLOSED=n SKIP=n
LNPORTF	monthly/annual	COBOL portfolio position & delinquent count.	reads LNLOAN	LNPORTF PRINCIPAL/ACCRUED/ARREARS/ESCROW/LOANS/DELINQUENT

C.2 Daily / weekly / monthly / annual detail

Daily — LNDAILY (LNACCRU → LNCASH → LNDELQP)

LNACCRU reads the run date from LNRUNDT (default 20260115), and for each active loan with a positive balance accrues balance × rate/1200 / 30 for the day — 4.00 on LN000001 — writing an LNACRD detail row (keyed LOANNO+ACDT) and, guarded by a stable ledger key, an LNTXN type-I row, then adding to LNACCR. LNCASH applies each unapplied receipt fees→interest→principal, surplus as a principal prepayment; a partial receipt clears interest before principal. LNDELQP re-ages each active loan by the days-past-due of its oldest billed-unpaid instalment (30/360 calendar) into buckets 0–4 and logs any movement to LNDELQ.

Expected DSPLY (one active 5000/12000-class loan accruing 4.00/day):
  LNACCRU ACCRUED=  1 SKIP=  3 TOT=      4.00
  LNCASH  APPLIED=  1 SKIP=  0            one receipt applied
  LNDELQP CHECKED=  4 MOVED=  0           book aged, nothing moved yet

Weekly — LNWEEK (LNARRWL → LNQUOTE → LNARRPR)

LNARRWL reads the delinquency logical file LNLOANL (which omits bucket-0 loans), totalling arrears (LNINTDU+LNPRNDU+LNFEE) by bucket. LNQUOTE prices a payoff per active loan: balance + (accrued + billed-unpaid interest) + fees - escrow, netting escrow off as a credit back to the borrower, and writes one LNQUOT row keyed (LOANNO, QTDT). LNARRPR prints the same worklist with borrower names and the payoff figure.

Expected payoff (LN000001 after month-1 billing, per the cycles suite):
  payoff = 12000.00 + (0.00 accrued + 120.00 billed) + 30.00 fees - 25.00 escrow = 12125.00

Monthly — LNMONTH (LNBILLP → LNFEEPG → LNGLPST → LNPORTF)

LNBILLP walks the schedule in due-date order via LNSCHDL, bills every S instalment due on or before the cut-off (default 20260201), moving its interest/principal into LNINTDU/LNPRNDU, relieving LNACCR by the interest billed (floored at 0), flipping the schedule row to B and posting an LNTXN type-B row. LNFEEPG totals the active fee catalogue by type and charges every billed loan the servicing fee (into LNFEE) and escrow (into LNFEE and LNESCRW both — a two-sided movement). LNGLPST sums the ledger and books the double entries. LNPORTF reports the book.

Expected DSPLY (the 4-loan seed book, month 1):
  LNBILLP BILLED=  4 SKIP=... TOT= 4480.00   4 x 1120.00-class instalments
  LNFEEPG CHARGED=  4 SKIP=... SVC=  5.00 ESC= 25.00  per-loan; book: fees 120.00, escrow 100.00
  LNGLPST BATCH=202602 ROWS=  6            DR/CR pairs: 480.00 interest, 120.00 fee+escrow
  LNPORTF LOANS ... 4  DELINQUENT ... 

Annual — LNYEAR (LNYRSTM → LNRATRV → LNCLOSE → LNPORTF)

LNYRSTM totals interest billed (ledger B rows), accrued (I) and fees (F) for the year-end certificate (INT=480.00 across the seed book). LNRATRV re-prices active loans against credit score: score ≥750 → original rate −1.0000 (floor 6.0000); score <600 → original rate +2.0000 (cap 30.0000); otherwise unchanged. The adjustment anchors on the original contracted rate (recovered from schedule instalment 1: interest/opening ×1200), never on the current rate, so the first run moves the rate and every re-run is a no-op. LNCLOSE settles any active zero-balance loan (all buckets zero): refunds the escrow via an LNTXN type-X row and flips status to S.

Expected DSPLY (per the cycles suite):
  LNYRSTM BILLED=  4 INT=    480.00 ACCR= 16.00 FEE=120.00
  LNRATRV CHECKED=  4 REPRICED=  2   780->11.0000 (down), 590->26.0000 (up)
  LNCLOSE CLOSED=  0 SKIP=  4         none fully repaid yet

C.3 Ordering & dependencies

• Within the daily cycle the CL fixes the order accrual → cash → re-bucket: interest must accrue before cash is applied to it, and delinquency re-bucketing must see the post-cash position.
• Origination before any servicing. LNORIG must build the schedule and activate the loan before accrual/billing have anything to act on.
• Billing (monthly) before delinquency ageing has teeth. LNDELQP ages the oldest billed-unpaid instalment, so a loan only becomes delinquent after LNBILLP has billed instalments that then go unpaid.
• Billing before fees. LNFEEPG charges only loans that have been billed (non-zero due buckets), so it must follow LNBILLP in the monthly CL.
• Cash before closure. LNCASH drives the balance to zero but does not settle; LNCLOSE (annual) does the settlement + escrow refund. Run the servicing that zeroes a loan before expecting the annual close to settle it.
• The run date advances the cycle. Because idempotency keys derive from the run date (accrual) or cut-off (billing), you must advance LNRUNDT to process a new period — see F.3.

D. Data Files (data dictionary) ↑ top

All files are in library AMORTIS, grounded in the DDS/SQL members in sources.mjs. Dates are stored as signed yyyymmdd numerics; money is packed 11P2; the nominal annual rate is packed 7P4 (12.0000 = 12%), wide enough that dividing by 12 keeps the periodic factor exact.

LNBRW — Borrower master (key BRWID, unique)

Field	Type	Meaning
BRWID	7A	Borrower id (key), e.g. BR00001.
BRNAME	30A	Borrower name.
BRADDR	30A	Address.
BRSCORE	4S 0	Credit score (read by the annual rate review).
BRSTAT	1A	A active, C closed.
BROPNDT	8S 0	Relationship-open date (yyyymmdd).

LNLOAN — Loan master (key LOANNO, unique)

Field	Type	Meaning
LOANNO	8A	Loan number (key), e.g. LN000001.
BRWID	7A	Owning borrower.
LNPRIN	11P 2	Original advanced principal.
LNRATE	7P 4	Nominal annual rate percent (12.0000 = 12%).
LNTERM	3S 0	Number of monthly instalments.
LNBAL	11P 2	Current principal outstanding.
LNACCR	11P 2	Interest accrued but not yet billed.
LNINTDU	11P 2	Interest billed and still unpaid.
LNPRNDU	11P 2	Principal billed and still unpaid.
LNESCRW	11P 2	Escrow balance held on the loan.
LNFEE	11P 2	Fees outstanding.
LNBUCK	1S 0	Delinquency bucket 0–4 (0 current, 4 = 90+).
LNDPD	5S 0	Days past due.
LNSTAT	1A	P pending, A active, S settled, W written off.
LNOPNDT / LNMATDT / LNNXTDT	8S 0	Opened / matures / next-due dates (yyyymmdd).

LNSCHD — Amortisation schedule (key LOANNO+SCHINS, unique)

Field	Type	Meaning
LOANNO / SCHINS	8A / 3S 0	Loan + instalment number (composite key).
SCHDUEDT	8S 0	Instalment due date (yyyymmdd).
SCHOPN	11P 2	Opening balance for the instalment.
SCHINT	11P 2	Interest component.
SCHPRN	11P 2	Principal component (constant, plug on the last).
SCHAMT	11P 2	Instalment = SCHINT + SCHPRN.
SCHCLS	11P 2	Closing balance = SCHOPN − SCHPRN.
SCHSTAT	1A	S scheduled, B billed, P paid.

Logical views: LNSCHDL keys the same records by SCHDUEDT, LOANNO (the monthly billing's due-date access path). LNLOANL keys LNLOAN by LNBUCK, LOANNO and omits bucket 0 (COMP(GT 0)) — the collections worklist is the file.

LNPAY — Payment receipts (key PYREF, unique)

Field	Type	Meaning
PYREF	8A	Receipt reference (key), e.g. PY000001.
LOANNO	8A	Loan the receipt is for.
PYDT / PYAMT	8S 0 / 11P 2	Receipt date / amount.
PYMETH	1A	Payment method.
PYSTAT	1A	U unapplied, A applied (applied once).

LNTXN — Transaction ledger (key TXSEQ, unique)

Field	Type	Meaning
TXSEQ	8S 0	Stable business-derived sequence (key; see F.2).
LOANNO	8A	Loan.
TXTYPE	1A	I accrual, B billing, C cash, F fee/escrow, S payoff, X closure.
TXDT / TXAMT	8S 0 / 11P 2	Transaction date / amount.
TXINT / TXPRN	11P 2	Interest / principal split of the amount.
TXBAL	11P 2	Balance snapshot after the txn (where applicable).
TXREF / TXMEMO	8A / 25A	Source reference / free-text memo.

LNACRD — Daily accrual detail (key LOANNO+ACDT, unique)

Field	Type	Meaning
LOANNO / ACDT	8A / 8S 0	Loan + accrual date (composite key — the accrual idempotency guard).
ACBAL	11P 2	Balance the accrual was computed on.
ACRATE	9P 6	Monthly factor applied (rate/1200).
ACAMT	11P 2	Interest accrued that day.

LNDELQ — Delinquency history (key DQSEQ, unique)

Field	Type	Meaning
DQSEQ	8S 0	Stable per (loan, resulting bucket) (key; range 70000000).
LOANNO / DQDT	8A / 8S 0	Loan / re-bucketing date.
DQOLD / DQNEW	1S 0	Bucket before / after.
DQDPD / DQAMT	5S 0 / 11P 2	Days past due / arrears at the move.

LNQUOT — Payoff quotations (key LOANNO+QTDT, unique)

Field	Type	Meaning
LOANNO / QTDT	8A / 8S 0	Loan + quote date (composite key; one quote per day).
QTPRIN / QTINT / QTFEE / QTESCR	11P 2	Principal / interest / fees / escrow components.
QTTOT	11P 2	Payoff total = prin + int + fee − escrow.
QTSTAT	1A	O open quotation.

LNFEE — Fee & escrow catalogue (key FECODE, unique)

Field	Type	Meaning
FECODE	4A	Fee code (key): SVC1, ESC1, LAT1.
FEDESC	25A	Description.
FETYPE	1A	S servicing fee (per instalment), E escrow contribution.
FEAMT	11P 2	Amount (SVC1 5.00, ESC1 25.00, LAT1 15.00).
FESTAT	1A	A active, I inactive (LAT1 is seeded inactive).

LNGLDIST — Interest-income GL distribution (SQL; PK GLSEQ)

Field	Type	Meaning
GLSEQ	DECIMAL(8,0)	Distribution row sequence (PK).
GLBATCH	DECIMAL(6,0)	Posting batch (yyyymm).
GLACCT / GLDRCR	CHAR(9) / CHAR(1)	Account (e.g. 4100-INTI) / D or C.
GLAMT	DECIMAL(11,2)	Posted amount.
GLLOAN / GLDT	CHAR(8) / DECIMAL(8,0)	Loan (or *ALL) / GL date.

Indexed by (GLACCT, GLDRCR) (LNGLDACC) so income by account is a keyed read.

Relationships

• LNLOAN.BRWID → LNBRW.BRWID (each loan owned by a borrower).
• LNSCHD.LOANNO → LNLOAN.LOANNO (schedule generated at origination; LNSCHDL/LNLOANL are logicals over LNSCHD/LNLOAN).
• LNPAY.LOANNO → LNLOAN.LOANNO (receipts against a loan; applied once).
• LNTXN / LNACRD / LNDELQ / LNQUOT all reference LOANNO (per-loan ledger, accrual, delinquency, quotes).
• LNFEE is a standalone catalogue; LNGLDIST is the SQL GL sink; LNRUNDT is the standalone run-date control.

E. Operations Runbook ↑ top

E.1 Day-in-the-life

1. One-time build (or after a rebuild): CALL AMORTIS/LNSETUP, then CALL AMORTIS/LNREFLD (seeds 4 borrowers, 3 fees, 4 pending loans), then CALL AMORTIS/LNORIG to build schedules and activate the loans.
2. Set today's accrual date: CHGDTAARA DTAARA(AMORTIS/LNRUNDT) VALUE(' <YYYYMMDD>') (the value is CHAR(10), right-justified).
3. Submit the daily cycle: SBMJOB CMD(CALL PGM(AMORTIS/LNDAILY)).
4. Post-check the daily run (below).
5. Handle interactive lookups through CALL AMORTIS/LNMENU (option 1 loan inquiry, option 2 the amortisation subfile) as needed.

Pre-checks: confirm the job's library list includes AMORTIS; confirm LNRUNDT holds the intended date (or is blank to accept the program default).

Post-checks after the daily cycle:

• LNACCRU ACCRUED= equals the count of active positive-balance loans; TOT= reconciles to their per-day interest (4.00 for each 12000@12% loan). Exactly one LNACRD row per loan per date; one LNTXN type-I row per loan per date.
• LNCASH APPLIED= equals the unapplied receipts; each waterfall obeyed fees→interest→principal (a 500.00 receipt on a loan owing 120.00 interest + 1000.00 principal retires the 120.00 first, then 380.00 principal).
• LNDELQP CHECKED= equals the active loans; MOVED= equals those that changed bucket, each with a matching LNDELQ row.

E.2 Month-end & year-end close

1. Confirm the month's daily cycles have all run.
2. Set the billing cut-off: CHGDTAARA DTAARA(AMORTIS/LNRUNDT) VALUE(' <month-end>').
3. Submit LNMONTH. Confirm LNBILLP BILLED=, LNFEEPG CHARGED=, LNGLPST ROWS=, and the LNPORTF lines.
4. At year end, submit LNYEAR and confirm the statement, rate review and closure lines.
5. Reconcile the ledger and GL (below).

Reconciling figures (the same ones the volume suites check against a hand-derived oracle, for the 4-loan seed book after month-1 billing):

• Interest billed — each loan bills 120.00 in month 1 (the LN000001/2/3/4 schedules all put 120.00 in instalment 1), so SUM(SCHINT) billed = 480.00; LNYRSTM INT=480.00 and GL 4100-INTI credited 480.00.
• Fees & escrow — 4 loans × 30.00 fee = 120.00 and 4 × 25.00 escrow = 100.00; GL 4200-FEEI credited with the 120.00 of fee+escrow the ledger recorded.
• Accrual relief — after billing, LNACCR is 0.00 (the 4.00 accrued was relieved by the 120.00 billed, floored at 0).
• Payoff quote — LN000001 = 12000.00 + 120.00 + 30.00 − 25.00 = 12,125.00; LN000003 = 6000.00 + 120.00 + 30.00 − 25.00 = 6,125.00.
• Rate review — BR00001 score 780 → LN000001 12.0000 down to 11.0000; BR00003 score 590 → LN000003 24.0000 up to 26.0000; LNRATRV REPRICED=2, and a re-run reprices 0.
• Portfolio — LNPORTF LOANS 4, with PRINCIPAL / ACCRUED / ARREARS / ESCROW totals summed straight off LNLOAN.

Ad-hoc portfolio & GL review: CALL AMORTIS/LNPORTF DSPLYs the book totals; STRSQL → SELECT GLACCT,GLDRCR,SUM(GLAMT) FROM AMORTIS.LNGLDIST GROUP BY GLACCT,GLDRCR proves the DR/CR pairs balance.

E.3 Failure & re-run rules

Each program DSPLYs a one-line result. Re-run safety is built on the stable idempotency keys (F.2): a re-run regenerates the same key, the CHAIN(EN) guard finds the existing row, and the program refuses to double-post.

Situation	Behaviour	Action
Re-run the daily accrual, same date	Each loan already has its LNACRD (LOANNO+ACDT) row and its ledger row.	Safe no-op — nothing double-accrues. Idempotent per accrual date. Advance LNRUNDT to accrue a new day.
Re-run cash application	The receipt is flipped to A; its ledger key (range 30000000) already exists.	Safe no-op — a receipt is applied exactly once.
Re-run monthly billing, same cut-off	Billed instalments are B; their ledger key (20000000) already exists.	Safe no-op — BILLED=0, the due bucket stays 120.00 (not 240.00).
Re-run fees	The fee ledger key (40000000) per loop already exists.	Safe no-op — CHARGED=0.
Re-run delinquency re-bucket	History key (70000000 + loan + resulting bucket) is stable per move.	No second history row for the same bucket; the loan is simply recomputed to the same value.
Re-run the annual rate review	The target is anchored to the original rate.	First run reprices, every re-run is REPRICED=0 — never walks the rate down repeatedly.
Re-run closure	An S loan is skipped; its closure ledger key (60000000) exists.	Safe no-op; a loan is never closed twice, and its escrow refunds exactly once.
Run a dated cycle without advancing LNRUNDT	The run date is unchanged, so the idempotency key is unchanged.	The cycle processes the same period again as a no-op. Always CHGDTAARA to a new date to process a new period (see F.3).

F. Developer Reference ↑ top

The complete program surface, from sources.mjs. All objects are in library AMORTIS. The RPG is written in the fixed-form C-spec / free-form hybrid the emulator's ibmi/samples.js convention uses; helpers C() and D() in sources.mjs emit column-exact C-spec and D-spec source.

F.1 Programs

LNREFLD (RPGLE) — reference-data seed

Writes 4 borrowers, 3 fee/escrow catalogue rows (SVC1/ESC1 active, LAT1 inactive) and 4 pending loans. DSPLYs LNREFLD BORROWERS=4 FEES=3 LOANS=4.

LNORIG (RPGLE) — origination

For each P loan, generates the constant-principal schedule (periodic factor rate/1200, principal advance/term, last-instalment plug), then re-CHAINs the loan and activates it (LNBAL=LNPRIN, LNSTAT='A'). Idempotent via the composite (LOANNO, SCHINS) KLIST guard.

LNACCRU (RPGLE) — daily accrual

Per active positive-balance loan: LNACCR += balance × rate/1200 / 30, one LNACRD (LOANNO+ACDT) row and one LNTXN type-I row (key range 10000000 + loan digits ×100 + day slot).

LNCASH (RPGLE) — payment application

Waterfall fees → interest → billed principal (also reduces LNBAL) → surplus principal prepayment. Ledger key range 30000000 + receipt digits; receipt flipped to A. Drives balance to zero but does not settle.

LNDELQP (RPGLE) — delinquency re-bucketing

Finds the oldest Billed-unpaid instalment, computes 30/360 days-past-due, maps to bucket 0–4, updates LNBUCK/LNDPD, and (on a move) writes LNDELQ.

LNBILLP (RPGLE) — monthly billing

Reads schedule in due-date order via LNSCHDL; bills each S instalment due ≤ cut-off, moves interest/principal to the due buckets, relieves LNACCR (floored 0), flips the row to B, posts LNTXN type-B (key 20000000).

LNFEEPG (RPGLE) — fees & escrow

Totals the active catalogue by type, charges every billed active loan the servicing fee (into LNFEE) and escrow (into LNFEE and LNESCRW), posts type-F (key 40000000).

LNGLPST (SQLRPGLE) — GL distribution

Sums LNTXN by type and inserts balanced DR/CR pairs into LNGLDIST with embedded EXEC SQL INSERT: interest (1210-INTR/4100-INTI), cash (1010-CASH/1200-LNRC), fee+escrow (1220-FEER/4200-FEEI).

LNQUOTE (RPGLE) — payoff quotation

Per active loan: balance + (accrued + billed-unpaid interest) + fees - escrow, one LNQUOT row keyed (LOANNO, QTDT).

LNARRWL / LNARRPR (RPGLE) — arrears worklist / print

Read LNLOANL (bucket-0 omitted), total arrears by bucket / print with borrower names and payoff. LNARRPR uses printer overflow (OFLIND(*IN90)) to re-print the header per page.

LNRATRV (RPGLE) — annual rate review

Recovers the original rate from schedule instalment 1 (SCHINT×1200/SCHOPN) and applies the score policy to that anchor. Idempotent by anchoring, not delta.

LNCLOSE (RPGLE) — matured closure

Settles an active zero-everything loan: refunds LNESCRW via type-X (key 60000000), sets LNSTAT='S'. Skips already-S loans.

LNYRSTM (RPGLE) — year-end statement

Totals ledger interest (B), accrual (I) and fees (F) for the tax certificate.

LNLOANIQ / LNSCHDIQ / LNMENU (RPGLE) — interactive

Loan-position screen with derived payoff; amortisation-schedule subfile (clear-then-load per enquiry); option menu dispatching to the two inquiries.

LNPORTF (ILE COBOL) — portfolio report

Sequential read of the keyed LNLOAN, DSPLYing PRINCIPAL / ACCRUED / ARREARS / ESCROW / LOANS / DELINQUENT totals.

LNSETUP / LNDAILY / LNWEEK / LNMONTH / LNYEAR (CL)

Build-and-compile; and the four cycles, each ADDLIBLE LIB(AMORTIS) then CALLing its members in the fixed order (section C).

F.2 The idempotency-key scheme

AMORTIS/i has no DB trigger layer; re-run safety is engineered into the ledger/detail keys. Each posting program derives a stable key from a business key plus a disjoint numeric range, so a re-run regenerates the SAME key, the CHAIN(EN) guard finds it, and the program refuses rather than double-posting.

Program	TXTYPE	Key formula
LNACCRU	I	10000000 + loan digits × 100 + accrual day-of-month slot
LNBILLP	B	20000000 + loan digits × 100 + instalment number
LNCASH	C	30000000 + receipt-reference digits
LNFEEPG	F	40000000 + loan digits × 100 + instalment number
LNCLOSE	X	60000000 + loan digits
LNDELQP	—	70000000 + loan digits × 10 + resulting bucket (into LNDELQ)

LNSCHD (composite LOANNO+SCHINS) and LNQUOT / LNACRD (composite LOANNO+date) are guarded through KLISTs rather than a single range — guarding on LOANNO alone would match instalment 1 and skip the whole loan.

F.3 The run-date data area (LNRUNDT)

Every dated batch program (LNACCRU, LNDELQP, LNBILLP, LNFEEPG, LNQUOTE) reads its processing date from a *CHAR(10) data area AMORTIS/LNRUNDT. If it holds a non-blank all-digit value, that is the date; otherwise the program falls back to a built-in default literal. The operator sets it with CHGDTAARA DTAARA(AMORTIS/LNRUNDT) VALUE(' YYYYMMDD') and blanks it to restore defaults.

F.4 Program-transaction (DSPLY) reference

Every batch program ends with a single DSPLY line the operator (and the test harness) reads as its result — the AMORTIS/i equivalent of a job-completion message. The full set:

Program	DSPLY line
LNREFLD	LNREFLD BORROWERS=n FEES=n LOANS=n
LNORIG	LNORIG ORIGINATED=n SKIP=n
LNACCRU	LNACCRU ACCRUED=n SKIP=n TOT=x
LNCASH	LNCASH APPLIED=n SKIP=n
LNDELQP	LNDELQP CHECKED=n MOVED=n
LNBILLP	LNBILLP BILLED=n SKIP=n TOT=x
LNFEEPG	LNFEEPG CHARGED=n SKIP=n SVC=x ESC=x
LNGLPST	LNGLPST BATCH=202602 ROWS=n
LNQUOTE	LNQUOTE QUOTED=n SKIP=n
LNARRWL	LNARRWL DELQ=n B1=x B2=x B3=x B4=x TOT=x
LNARRPR	LNARRPR LINES=n TOT=x
LNRATRV	LNRATRV CHECKED=n REPRICED=n
LNCLOSE	LNCLOSE CLOSED=n SKIP=n
LNYRSTM	LNYRSTM BILLED=n INT=x ACCR=x FEE=x
LNPORTF	LNPORTF PRINCIPAL/ACCRUED/ARREARS/ESCROW/LOANS/DELINQUENT <value> (six lines)

G. Glossary ↑ top

Amortisation schedule (LNSCHD)

The per-instalment plan generated at origination: opening balance, interest, principal, instalment and closing balance for each of the loan's instalments.

Constant-principal (straight-line)

An amortisation where the principal component of every instalment is fixed (advance/term) and the interest declines with the balance; the instalment declines. AMORTIS/i's chosen model, exact to the cent with a final-instalment plug when the advance does not divide evenly.

30/360

The day-count convention: every month is 30 days, every year 360. A day of interest is balance × rate/1200 / 30; a 30-day month accrues exactly the schedule's interest.

Accrual (LNACCR / LNACRD)

Interest recognised each day on the outstanding balance, added to the loan's unbilled accrual bucket and audited row-by-row in LNACRD; relieved when the instalment is billed.

Payment waterfall

The order a receipt is applied by LNCASH: fees, then interest, then billed principal, then any surplus as a principal prepayment.

Delinquency bucket (LNBUCK)

0 current, 1 = 1–29 days past due, 2 = 30–59, 3 = 60–89, 4 = 90+, off the oldest billed-unpaid instalment.

Payoff quotation (LNQUOT)

The price to settle a loan today: principal + accrued + billed-unpaid interest + fees − escrow (escrow returned to the borrower).

Escrow (LNESCRW)

Money collected from the borrower and held on the loan; a two-sided movement at billing and refunded at closure.

Idempotent

Safe to run again with the same result. Here achieved by deriving a stable ledger/detail key from a business key and refusing to re-post via CHAIN(EN); and, for the rate review, by anchoring on the original rate.

Anchoring (rate review)

Applying an adjustment to the loan's ORIGINAL contracted rate (recovered from schedule instalment 1), not the current rate — so a re-run does not walk the rate away.

Run-date data area (LNRUNDT)

The *CHAR(10) data area holding the processing date the dated batch programs read, set by CHGDTAARA, so a parameterless cycle can be driven for any period.

SBMJOB / CHGDTAARA / DSPLY

Submit Job; Change Data Area (set the run date); and the RPG operation each program uses to emit its one-line result.

Ledger (LNTXN)

The durable transaction trail every posting program contributes to: types I accrual, B billing, C cash, F fee/escrow, S payoff, X closure.

GL distribution (LNGLDIST)

The SQL table LNGLPST writes balanced double entries into: interest, cash and fee/escrow DR/CR pairs by account.