The characteristics that shape every migration off this platform.
Non-Unicode codepagesMany R/3 installations were never converted to Unicode. Text sits under a legacy codepage, so extended characters need explicit conversion on extract. Skip it and names and addresses arrive corrupted — while every record count still reconciles, because the row is there and only its contents are wrong.
Classic G/L rather than New G/LR/3 typically runs classic General Ledger: no document splitting, totals maintained separately from line items, segment reporting through special ledgers. The financial model being read is not the one a modern target expects.
MANDT — client partitioningAs in ECC, application tables are client-dependent and an unconstrained extract blends clients.
ADK archive filesData already archived out of R/3 lives in ADK archive files, not the database. If that history is in scope it must be read through the archive layer — a common late discovery on legacy estates.
Custom Z-tables and modificationsA long-running R/3 estate accumulates custom tables and modified standard objects holding data the business depends on. Profiling finds them; a standard object list does not.
Older extraction toolchainR/3 predates the modern integration surface. Extraction generally means ABAP extract programs or database-level reads rather than OData services.