# Enterprise Data Migration & Cutover Runbook ## 1. Master Cutover Chronology (T-Minus to Cutover) * **T-04:00 (Pre-Flight):** Verify AWS DMS CDC replication lag is under 2 seconds; freeze source reporting cron jobs. Owner: Lead DBA. * **T-00:00 (Maintenance Start - 10:00 PM):** Put source Oracle instance into read-only mode; terminate active application connection pools. Owner: Infrastructure Lead. * **T+01:30 (Drain CDC & Sync):** Drain remaining Oracle redo logs through AWS DMS; verify LSN alignment on Aurora PostgreSQL. Owner: Migration Engineer. * **T+03:00 (Go/No-Go Gate 1):** Execute automated ledger balance checksums; if delta exceeds 0.00%, abort to rollback procedure. Owner: Program Director. * **T+04:30 (Index & FK Build):** Enable secondary indexes and foreign key constraints on target Aurora cluster in parallel threads. Owner: Lead DBA. * **T+06:00 (Application Re-point):** Update route 53 DNS records and Kubernetes database connection secrets to Aurora endpoints; commence smoke testing. Owner: DevOps Lead. --- ## 2. ETL Schema Transformation & Mapping Matrix | Source Entity (Oracle) | Target Entity (Aurora PG) | Type Conversion | Transformation Rule | | :--- | :--- | :--- | :--- | | `LEDGER_ENTRY.ID` | `ledger_entry.id` | `NUMBER(19)` to `BIGINT` | Direct identity mapping | | `LEDGER_ENTRY.AMOUNT` | `ledger_entry.amount` | `NUMBER(15,2)` to `NUMERIC(15,2)` | Exact precision retention | | `DOCUMENT_BLOB.DATA` | `document_blob.data` | `BLOB` to `BYTEA` | Streamed hex conversion | | `USER_PII.SSN` | `user_pii.ssn` | `VARCHAR2(11)` to `TEXT` | KMS AES-256 runtime encryption | --- ## 3. Automated Rollback Protocol * **Abort Trigger:** CDC replication stall > 45 minutes past T+02:00, or failure of financial sum parity check at T+03:00. * **Recovery Sequence:** 1. Revoke read-only flag on Oracle 19c (`ALTER SYSTEM SET READ_ONLY = FALSE`). 2. Restore application DNS routing to legacy Exadata endpoints. 3. Purge incomplete migration staging tables on Aurora target. --- ## 4. Data Parity & Reconciliation Audit Framework * **Row Parity:** Query `pg_class` against Oracle `DBA_TABLES` across all 420 tables via Python verification script. * **Ledger Checksum:** Compute MD5 hash aggregates of debits and credits grouped by fiscal quarter across both environments. * **Compliance Audit:** Validate that all sensitive columns return masked ciphertext strings on Aurora before user access is restored.