RFC Protocol Deep Dive

This comprehensive guide covers the RFC (Remote Function Call) protocol in ERPL. Learn how to read SAP tables, call function modules, and handle metadata like a pro.

What is RFC?

RFC (Remote Function Call) is SAP's protocol for calling functions across system boundaries. It's the foundation of SAP integration and allows you to access SAP tables and execute function modules remotely.

RFC Architecture

Core RFC Functions

sap_read_table()

The primary function for reading SAP tables.

-- Basic table reading
SELECT * FROM sap_read_table('KNA1', MAX_ROWS => 100);

-- With field selection
SELECT KUNNR, NAME1, LAND1 
FROM sap_read_table('KNA1', MAX_ROWS => 50);

-- With WHERE conditions
SELECT * FROM sap_read_table('VBAK', MAX_ROWS => 100)
WHERE ERDAT >= '2024-01-01';

Parameters

Parameter	Type	Description	Example
table_name	VARCHAR (positional)	SAP table name	'KNA1'
COLUMNS	LIST(VARCHAR)	Restrict to a subset of columns	COLUMNS => ['KUNNR', 'NAME1']
FILTER	VARCHAR	OpenSQL-style WHERE-fragment passed straight to RFC. Use for filters too complex to push down.	FILTER => 'LAND1 = ''DE'''
MAX_ROWS	UINTEGER	Maximum rows to return	MAX_ROWS => 1000
THREADS	UINTEGER	Number of parallel RFC threads (default: 5)	THREADS => 4
READ_TABLE_FUNCTION	VARCHAR	Override the underlying RFC function module (e.g. /SAPDS/RFC_READ_TABLE2 for wide rows)	READ_TABLE_FUNCTION => '/SAPDS/RFC_READ_TABLE2'
READ_TABLE_DELIMITER	VARCHAR	Delimiter RFC uses when packing rows. Override for tables whose values may contain whitespace.	`READ_TABLE_DELIMITER => '
SECRET	VARCHAR	Name of the DuckDB secret to authenticate with	SECRET => 'erp_prod'

Predicate and projection pushdown

A regular SQL WHERE clause is pushed down to RFC automatically — you don't need the FILTER named parameter for simple predicates. COLUMNS is inferred from the SELECT list:

SELECT KUNNR, NAME1 FROM sap_read_table('KNA1') WHERE LAND1 = 'DE';

Reach for the named parameters when you need precise control over what RFC receives — for example, complex multi-table filters that DuckDB's optimizer can't safely lower.

Ordering

RFC's underlying RFC_READ_TABLE has no server-side sort. Apply ORDER BY in DuckDB after the read; it executes client-side.

sap_rfc_invoke()

Call SAP function modules and BAPIs. Input parameters are passed as positional struct arguments after the function name — one struct per import / changing parameter the BAPI expects. DuckDB struct syntax ({'KEY': value, ...}) lets you express nested structures and tables naturally.

-- Simple function module with one import struct
SELECT trim(ECHOTEXT)
FROM sap_rfc_invoke('STFC_CONNECTION', {'REQUTEXT': 'Hello'});

-- BAPI returning a sub-table — pick it via path
SELECT *
FROM sap_rfc_invoke(
  'BAPI_FLIGHT_GETLIST',
  {'AIRLINE': 'LH', 'DESTINATION_FROM': {'AIRPORTID': 'FRA'}},
  path => '/FLIGHT_LIST'
);

-- BAPI with nested import + path selection
SELECT *
FROM sap_rfc_invoke(
  'BAPI_FLIGHT_GETDETAIL',
  {'AIRLINEID': 'LH', 'CONNECTIONID': '0400', 'FLIGHTDATE': '2016-11-18'::DATE}
);

Parameters

Parameter	Type	Description	Example
function_name	VARCHAR (positional)	SAP function module / BAPI name	'BAPI_FLIGHT_GETLIST'
parameters...	STRUCT (positional varargs)	One struct per RFC import/changing parameter	{'AIRLINE': 'LH'}
path	VARCHAR (named)	Optional path into the response structure — picks a sub-table of the result	path => '/FLIGHT_LIST'
secret	VARCHAR (named)	Name of the DuckDB secret to authenticate with	secret => 'erp_prod'

sap_rfc_describe_function()

Get detailed information about RFC function parameters.

-- Describe function parameters
SELECT * FROM sap_rfc_describe_function('BAPI_FLIGHT_GETLIST');

-- Get parameter details
SELECT 
  name,
  import[1].name AS import_params,
  export[1].name AS export_params
FROM sap_rfc_describe_function('STFC_CONNECTION');

sap_describe_fields()

Get table structure and field information. The result columns are pos, is_key, field, text, sap_type, length, decimals, check_table, ref_table, ref_field, and language.

-- Get table structure
SELECT * FROM sap_describe_fields('KNA1');

-- Get field details for a specific table
SELECT
  field,
  text,
  sap_type,
  length,
  decimals
FROM sap_describe_fields('VBAK');

sap_rfc_authorizations()

Document which RFC function module each ERPL function calls — useful when requesting RFC authorizations from SAP Basis. Returns extension, duckdb_function, rfc_function_module, invocation, and purpose.

-- Every RFC module ERPL may invoke
SELECT * FROM sap_rfc_authorizations();

-- Just the distinct module names used by the RFC extension
SELECT DISTINCT rfc_function_module
FROM sap_rfc_authorizations()
WHERE extension = 'erpl_rfc';

sap_rfc_show_function()

List all available RFC functions.

-- List all RFC functions
SELECT * FROM sap_rfc_show_function();

sap_rfc_show_groups()

List all RFC function groups.

-- List all function groups
SELECT * FROM sap_rfc_show_groups();

sap_show_tables()

List all available SAP tables.

-- List all tables
SELECT * FROM sap_show_tables();

Common SAP Tables

Master Data Tables

-- Customer Master Data
SELECT 
  KUNNR AS customer_number,
  NAME1 AS customer_name,
  LAND1 AS country,
  REGIO AS region,
  ORT01 AS city
FROM sap_read_table('KNA1', MAX_ROWS => 1000)
WHERE LAND1 = 'DE';

-- Material Master Data
SELECT 
  MATNR AS material_number,
  MTART AS material_type,
  MEINS AS base_unit,
  MATKL AS material_group
FROM sap_read_table('MARA', MAX_ROWS => 1000)
WHERE MTART = 'FERT';  -- Finished goods

-- Vendor Master Data
SELECT 
  LIFNR AS vendor_number,
  NAME1 AS vendor_name,
  LAND1 AS country,
  REGIO AS region
FROM sap_read_table('LFA1', MAX_ROWS => 1000);

Transaction Data Tables

-- Sales Document Header
SELECT 
  VBELN AS sales_document,
  ERDAT AS document_date,
  KUNNR AS customer,
  NETWR AS net_value,
  WAERK AS currency
FROM sap_read_table('VBAK', MAX_ROWS => 1000)
WHERE ERDAT >= '2024-01-01';

-- Sales Document Items
SELECT 
  VBELN AS sales_document,
  POSNR AS item_number,
  MATNR AS material,
  KWMENG AS quantity,
  NETWR AS net_value
FROM sap_read_table('VBAP', MAX_ROWS => 1000)
WHERE VBELN IN ('0000000001', '0000000002');

Financial Tables

-- Accounting Document Header
SELECT 
  BUKRS AS company_code,
  BELNR AS document_number,
  GJAHR AS fiscal_year,
  BLART AS document_type,
  BUDAT AS posting_date
FROM sap_read_table('BKPF', MAX_ROWS => 1000)
WHERE GJAHR = '2024';

-- Accounting Document Items
SELECT 
  BUKRS AS company_code,
  BELNR AS document_number,
  GJAHR AS fiscal_year,
  BUZEI AS line_item,
  HKONT AS gl_account,
  DMBTR AS amount_in_local_currency
FROM sap_read_table('BSEG', MAX_ROWS => 1000)
WHERE HKONT LIKE '1%';  -- Asset accounts

Advanced RFC Techniques

Metadata Handling

-- Get table structure
SELECT * FROM sap_describe_fields('KNA1');

-- Get function module parameters
SELECT * FROM sap_rfc_describe_function('BAPI_CUSTOMER_GETDETAIL');

-- List all available functions
SELECT * FROM sap_rfc_show_function();

-- List function groups
SELECT * FROM sap_rfc_show_groups();

-- List all tables
SELECT * FROM sap_show_tables();

Batch Processing

-- Process multiple tables in one call
SELECT 
  'KNA1' AS table_name,
  COUNT(*) AS record_count
FROM sap_read_table('KNA1', MAX_ROWS => 10000)

UNION ALL

SELECT 
  'VBAK' AS table_name,
  COUNT(*) AS record_count
FROM sap_read_table('VBAK', MAX_ROWS => 10000);

Reading function output and errors

sap_rfc_invoke returns the function module's actual export/table parameters as columns — there are no synthetic return_code/error_message columns. For RFC_SYSTEM_INFO, the export parameter is the RFCSI_EXPORT struct, so you read fields out of it:

-- System info is returned as the RFCSI_EXPORT struct
SELECT
  RFCSI_EXPORT.rfcsysid AS system_id,
  RFCSI_EXPORT.rfchost  AS host,
  RFCSI_EXPORT.rfcsaprl AS release
FROM sap_rfc_invoke('RFC_SYSTEM_INFO');

For BAPIs, error status lives in the BAPI's own RETURN table (BAPIRET2). Select it with the path parameter and filter on its TYPE column ('E' = error, 'A' = abort):

SELECT *
FROM sap_rfc_invoke('BAPI_SOME_METHOD', {'KEY': 'VALUE'}, path => '/RETURN')
WHERE TYPE IN ('E', 'A');

Performance Optimization

Mounting SAP tables as a catalog

ERPL caches and reuses RFC connections per secret automatically — there is no separate connection-pool object to configure. If you want SAP tables to appear as a browsable schema (so you can write sap.KNA1 instead of sap_read_table('KNA1')), ATTACH a sap_rfc catalog. Use the TABLES option to limit which tables are exposed:

-- Mount selected SAP tables as the "sap" catalog
ATTACH '' AS sap (TYPE sap_rfc, SECRET 'my_sap', TABLES 'KNA1,VBAK,MARA');

-- Query them like local tables (still read over RFC, with push-down)
SELECT KUNNR, NAME1 FROM sap.KNA1 WHERE LAND1 = 'DE';
SELECT * FROM sap.VBAK LIMIT 100;

Parallel Processing

-- Read multiple tables in parallel
SELECT 'KNA1' AS table_name, COUNT(*) AS count
FROM sap_read_table('KNA1', MAX_ROWS => 10000)

UNION ALL

SELECT 'VBAK' AS table_name, COUNT(*) AS count
FROM sap_read_table('VBAK', MAX_ROWS => 10000)

UNION ALL

SELECT 'MARA' AS table_name, COUNT(*) AS count
FROM sap_read_table('MARA', MAX_ROWS => 10000);

Real-World Examples

Daily Sales Report

-- Extract daily sales data
WITH daily_sales AS (
  SELECT 
    ERDAT AS sales_date,
    COUNT(*) AS order_count,
    SUM(NETWR) AS total_value,
    AVG(NETWR) AS avg_order_value
  FROM sap_read_table('VBAK', MAX_ROWS => 100000)
  WHERE ERDAT >= CURRENT_DATE - INTERVAL '30' DAY
  GROUP BY ERDAT
)
SELECT 
  sales_date,
  order_count,
  total_value,
  avg_order_value,
  ROUND(avg_order_value, 2) AS avg_order_value_rounded
FROM daily_sales
ORDER BY sales_date DESC;

Customer Analysis

-- Analyze customer distribution by country
SELECT 
  LAND1 AS country,
  COUNT(*) AS customer_count,
  COUNT(*) * 100.0 / SUM(COUNT(*)) OVER() AS percentage
FROM sap_read_table('KNA1', MAX_ROWS => 100000)
GROUP BY LAND1
ORDER BY customer_count DESC
LIMIT 10;

Material Master Analysis

-- Analyze material types and groups
SELECT 
  MTART AS material_type,
  MATKL AS material_group,
  COUNT(*) AS material_count
FROM sap_read_table('MARA', MAX_ROWS => 100000)
GROUP BY MTART, MATKL
ORDER BY material_count DESC
LIMIT 20;

Troubleshooting

Common Issues

Table Not Found

-- Check table name (case-sensitive)
-- Verify table exists in your SAP system
SELECT * FROM sap_read_table('KNA1', MAX_ROWS => 1);

Permission Denied

-- Verify RFC access rights by calling a low-privilege function
SELECT * FROM sap_rfc_invoke('RFC_SYSTEM_INFO');

Connection Timeout

Configure timeouts via the sap_rfc secret options when creating the secret:

CREATE SECRET my_sap (
  TYPE sap_rfc,
  ASHOST 'your-host',
  SYSNR '00',
  USER 'username',
  PASSWD 'password',
  CLIENT '100',
  LANG 'EN'
);

Debugging Tips

-- Ping the SAP system (pragma — no result rows; raises on failure)
PRAGMA sap_rfc_ping;

-- Monitor query performance
EXPLAIN SELECT * FROM sap_read_table('KNA1', MAX_ROWS => 100);

-- Smoke-test the RFC pipeline
SELECT * FROM sap_rfc_invoke('RFC_SYSTEM_INFO');

For SAP Experts

For SAP Basis administrators and developers: the binary RFC transport, performance characteristics, and security model. Expand the internals below.

RFC protocol internals — transport, performance, security

RFC Protocol Details

ERPL uses the proprietary SAP NetWeaver RFC SDK, which speaks SAP's binary RFC protocol (CPIC over TCP/IP) — the same library SAP GUI and other SAP tools use. Characteristics:

• Connection: direct application-server logon (ASHOST + SYSNR) via the SAP Gateway (port 33NN, where NN is the instance number), or message-server/load-balanced logon (MSHOST + GROUP)
• Protocol: binary RFC over TCP/IP (not HTTP)
• Authentication: user/password, or SNC (Secure Network Communication) for certificate-based, encrypted logon
• Transport security: SNC, or an SSH tunnel on untrusted networks
• Unicode: full Unicode support

All of this is configured through the DuckDB sap_rfc secret — the same secret used by the BICS and ODP extensions, which ride on the same RFC transport.

Performance Considerations

1. Connection reuse: ERPL caches RFC connections per secret — keep work in one session
2. Row cap: bound large reads with MAX_ROWS, and tune THREADS for your network
3. Field selection: use COLUMNS => [...] (or rely on SELECT-list projection push-down) to reduce data transfer
4. Filter push-down: a plain WHERE clause is lowered to RFC; use FILTER for predicates the optimizer can't push

Security Best Practices

1. Network Security: Use VPN or secure network connections
2. Authentication: Use strong passwords or certificates
3. Authorization: Implement proper RFC user roles
4. Audit Logging: Enable RFC audit logs in SAP

Next Steps

🚀 Ready for More?

• BICS Protocol Guide - Execute SAP BW queries
• ODP Protocol Guide - Delta replication
• Function Reference - Complete API docs

🔧 Advanced Topics

• RFC Metadata Guide - Discover SAP functions and tables
• Performance Tuning - Optimize RFC calls
• Real-World Use Cases - Complete scenarios

💡 Examples

• ERPL Examples - More real-world RFC examples
• Integration with Python - Use RFC data with Pandas

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Need help? Check our troubleshooting guide or browse more examples.