Source-derived document; review findings and open questions with the application owner.

Phase 4: Understanding Handoff

Purpose and Evidence Boundary

This handoff consolidates the current understanding of a partially reconstructed CardDemo mainframe system. The evidence establishes artifacts, stated relationships, and intended behavior, but not successful execution, complete topology, compiler semantics, sequencing, production behavior, or semantic completeness. Conflicting evidence about whether all artifacts execute together must remain visible. E0001 E0010 E0017 E0020 E0021 E0002 E0003 E0005 E0006 E0018

Current-System Understanding

The observed functional scope includes accounts, customers, cards, transactions, security, authorization, fraud, reporting, migration, statements, interest, fees, and rejection handling. Online functions include login, inquiry, maintenance, payment, and reporting; batch and utility functions include posting, VSAM processing, date conversion, compilation, migration, backups, and `REPRO`. These capabilities are described by the evidence but are not uniformly confirmed as operational. E0002 E0003 E0005 E0006 E0027 E0038 E0039 E0040 E0041 E0042 E0043 E0012 E0022 E0024

Inference: The evidence most strongly describes a configured, partially reconstructed IBM mainframe architecture expressing intended design rather than a complete behavioral model. This is an interpretation of the evidence, not proof of deployment or runtime behavior. E0023 E0037 E0038 E0041 E0045 E0046

Actors, Security, and Operations

Regular users, administrators, operators, and a Control-M scheduler environment on UNIX at `MY-HOST` are identified. Ownership, role boundaries, permissions, and enforcement are not established. Authentication-related evidence includes the login transaction, `USRSEC`, RACF, and `DUSRSECJ`; encryption, masking, authorization enforcement, auditing, queue permissions, and network boundaries remain unknown. E0026 E0028 E0035 E0036 E0044 E0047 E0001 E0016 E0032 E0033 E0040

Operational evidence covers scheduling, waits, reruns, backups, GDGs, indexing, reporting, logging, rollback, abends, SQL handling, and internal-reader submission. Monitoring, alerting, restart, disaster recovery, ownership, atomicity, and completion guarantees are unknown; two-phase commit is disputed. E0015 E0028 E0031 E0039 E0044 E0045

Processing Journeys and Decisions

The sign-on journey validates credentials and routes administrators to administrative processing and other users to menu processing through `XCTL`. Payment processing uses account data for lookup and balance validation, while transaction processing writes validated input and reports failed validations to a rejection file. Other journeys include administrative dispatch, batch posting, reporting, VSAM loading and indexing, compilation, backup, and `REPRO`. Mappings, sequencing, restoration, and runtime outcomes remain incomplete. E0034 E0038 E0029 E0007 E0008 E0030 E0031 E0046 E0025

Observed decisions include add, update, delete, view, list, cancel, page, submit, approve, decline, accept, reject, and fraud insertion or duplicate-key update. Inference: validation appears intended to separate processing from rejection, but decision ownership, rationale, and complete return-code semantics are unknown. E0003 E0010 E0022 E0025 E0028 E0038 E0011 E0013 E0041 E0042

Components, Data, and Relationships

The component set includes CICS programs and maps, copybooks, VSAM KSDSs and indexes, DB2 and IMS artifacts, MQ flows, batch programs, JCL, GDGs, REXX, reports, and data-model diagrams. Explicit evidence connects account, customer, card, security, transaction, reporting, and migration components to named files, datasets, procedures, or transactions. It also identifies optional transaction-type management across DB2 and VSAM, with a stated category-to-type foreign-key relationship and restricted deletion. E0006 E0019 E0026 E0035 E0047 E0010 E0011 E0016 E0017 E0020 E0021 E0022 E0024 E0025 E0042 E0046

Information includes accounts, customers, cards, users, transactions, authorization, fraud, classifications, cross-references, reports, statements, and imports or exports. Layout, encoding, timestamps, index offsets, naming, and an unresolved six-byte unload discrepancy remain open. Duplicate, malformed, stale, contradictory, or incomplete artifacts are risks identified by the evidence, not confirmed defects. E0004 E0009 E0010 E0021 E0037 E0043 E0045 E0006 E0019 E0026 E0035 E0047

Interfaces and External Dependencies

Interfaces include CICS, BMS, `XCTL`, commareas, VSAM, MQ, IMS, DB2, JCL, TDQs, REXX, FTP, sorting, and reporting tools. Contracts, keys, transformations, queues, and runtime compatibility are unresolved. Named external dependencies include CICS, DB2, IMS, MQ, VSAM, RACF, JES/TSO, SDSF, IDCAMS, UNIX, Control-M, FTP, CEEDAYS, and an Ensono-hosted mainframe. Topology, ownership, availability, and actual integration are unknown; z/OS and AWS interpretations are inferences. E0001 E0003 E0007 E0035 E0039 E0046 E0003 E0018 E0026 E0038 E0042

Rules, States, and Hazards

Observed states include validation, confirmation, routing, acceptance, rejection, approval, decline, end-of-file, concurrent update, backup, error, abend, deployment, and generation increments. Rules address credentials, validation, dates, balances, expiry, limits, duplicate handling, referential integrity, paging, retention, return codes, interest, fees, and deletion. Fraud criteria, rates, checksums, filtering, and complete rule semantics remain unknown. `COND=(4,LT)` is disputed under ordinary JCL interpretation. E0015 E0017 E0018 E0045 E0011 E0013 E0026 E0027 E0041 E0042

Potential hazards include destructive replacement or recreation, partial updates, ineffective conditions, malformed input, unstable paging, duplicate IDs, inconsistent indexes, exposed credentials, FTP failure, critical VSAM errors, and abends. No incident is established, and complete recovery behavior is unknown. E0001 E0006 E0014 E0018 E0019 E0026 E0037 E0040 E0042

Handoff Unknowns and Required Caution

The next phase must not assume complete schemas, mappings, actors, ownership, security controls, deployment topology, sequencing, business rules, balances, calculations, configuration, restart and recovery, retention, external contracts, version alignment, or production suitability. Conflicts concerning PF7, maps, copybooks, deployed artifacts, source coverage, and diagram meaning remain unresolved. E0009 E0011 E0014 E0017 E0020 E0021 E0025 E0036 E0039 E0047

Unknown: Successful end-to-end execution and semantic completeness are not established by the supplied evidence. E0001 E0010 E0020 E0021