Oracle — Instant Client Odbc

Application (e.g., PowerBI, R, C++ app) ↓ (ODBC API calls: SQLConnect, SQLExecDirect) Oracle Instant Client ODBC Driver (sqora32.dll) ↓ (OCI calls: OCIHandleAlloc, OCIStmtExecute) Oracle OCI Library (oci.dll) ↓ (Oracle Net Services - TNS protocol) Network (TCP/IP) ↓ Oracle Database Server (Listener + Background Processes)

This is Oracle's crown jewel. If a database node fails mid-transaction, TAF allows the driver to automatically reconnect to a surviving node and replay idle connections. For ODBC applications, this is configured via FAILOVER=ON and RETRY_COUNT . However, note the limitation: TAF cannot replay a transaction that was in the middle of an uncommitted update. The application will receive SQL_ERROR with state 08006 (connection failure) for the current statement, but subsequent statements on the same handle will work on the new node. oracle instant client odbc