SAP RFC errors
RFC errors break integration between SAP and other systems. This page covers diagnosing common RFC connection and call failures.
When an interface, BAPI call or IDoc distribution fails with a communication or logon error, start in SM59 and run the destination's connection and authorization tests, then read SM21 and ST22 on the target. The causes come in order: unreachable host or port, a wrong or locked service user, missing authorizations, then the gateway or SNC.
- Watch out: connection failed and logon failed are different layers, and the message tells you which.
Symptom
An interface, BAPI call or IDoc distribution fails with a communication or logon error.
Start here: read the evidence
Start in SM59: run the connection and authorization test for the destination. Check the target system’s logs (SM21, ST22) and, for the interface, the relevant monitor (IDoc/qRFC). The error text usually distinguishes network, logon and authorization problems.
Likely causes, in order
- Network/host, target unreachable (host/port/firewall).
- Logon failed, wrong credentials or locked service user.
- Authorization, the RFC user lacks rights in the target.
- Gateway/security, blocked registered program or SNC issue.
How to fix it
- Run the SM59 connection and authorization tests.
- Verify host/port/network reachability to the target.
- Check the service user (valid, unlocked, right authorizations).
- Fix the destination or target-side authorization; re-test.
Preventing recurrence
Use least-privilege service users and secure the gateway. After a system copy, correct destinations that still point at the source. Monitor interfaces so RFC failures are caught before they back up.
Common pitfalls
- Guessing instead of reading the log/dump.
- Fixing the symptom, not the root cause.
- Changing several things at once.