LEARN. PRACTICE. GROW.Preserve invariants during migration
The requirement for one authorized writer per account applies throughout the interval, not only in the final state. If old and new systems write simultaneously for two minutes, later reconciliation does not establish exclusivity. The design needs to explain authority transfer, and the rehearsal must observe that behavior. Technical alternatives may exist, but selection depends on requirements, failures and context. Do not automatically turn later convergence into acceptance of concurrent writing: that would change the approved condition and require its own decision.
Calculate the return-decision limit
The exercise requires validated operation by 18:00. Returning takes fifteen minutes and validation takes ten sequential minutes. Subtracting 25 minutes gives 17:35 as the latest feasible time without additional buffer. At 17:30, allowing ten further minutes of repair would move completion to 18:05. The plan should make authority, conditions and the decision limit visible. In production, use justified durations and buffer appropriate to context; this example is not a universal recommendation. A written procedure does not eliminate execution time.
Separate a gate, failure and unknown information
When the agreement requires demonstrated connectivity, reconciliation and recovery, two positive conditions do not form a sufficient majority. If the recovery result is missing, the gate remains unproven. That also does not establish that recovery is impossible: it is an evidence gap. Report the condition, owner and what is needed to decide. The same care applies to coverage: a 1 GB file rehearsal at low load does not automatically demonstrate a 1-to-5 GB closing requirement. The test-requirement link should include relevant conditions.
Connect cost and recovery to scope
Over three months, the baseline would cost €120k for the old platform. Retaining old and new costs €195k, plus €20k migration: €215k total and €95k increase. Do not confuse total with difference. Recovery scope matters too: parallel branches of 14 and 20 minutes followed by five validation minutes give 25 service minutes. Comparing only components with a 22-minute RTO would hide a three-minute gap. Both models depend on the relationships and exclusions explicitly supplied rather than on universal cost or recovery rules.
Maintain decisions when context changes
An ADR proposal with pending actions does not replace an accepted decision. In the illustrative AWS process, preserve context and consequences and complete review before treating a new decision as accepted. Operational authorization still follows the relevant process. Context changes may require reassessment even without technical failure: per-core licensing announced for 120 days later may change cost and options across five applications. Identify dependencies, financial and technical owners, and transition time. Do not necessarily wait for the first incident to revisit architecture suitability.
Exercise: a recommendation sensitive to preferences
Calculate w×cost+(1−w)×fitness, with higher scores always better. X has 90/60 and Y 60/90. At w=0.4, X=72 and Y=78; at w=0.6, X=78 and Y=72. The tie occurs at 0.5. Selection depends on an unresolved preference; do not invent official TOGAF weights or hide the reversal. Prepare a committee package covering missing requirements, delay impact, authority and decisive evidence. Practice uses internal binary marking; it neither reproduces gradient scoring nor awards the Practitioner qualification.
At 17:30, draw a timeline to 18:00. Mark decision at 17:35, return by 17:50 and validation by 18:00. Explain what changes if return needs twenty minutes or additional buffer is required.
Common pitfalls
Consuming the return window through successive attempts; approving a gate by majority; calling unknown information a failure; adding parallel branches; omitting validation; using an ADR proposal as an accepted decision.
Related topics: E/F planning and G governance · Requirements and evidence management · H change and ADR decisions
Acceptance should correspond to the requirement, state and evidence that actually exist. Time limits and dependencies need to appear in the plan before execution pressure dominates the decision.
Reference: Practitioner competency-to-role mapping · OGEA-102; TOGAF Standard, 10th Edition