tRFC / qRFC Submit

Use transactional RFC (tRFC) when you need exactly-once delivery of an RFC call — the SAP system deduplicates calls by a transaction ID (TID) so that retries after a network failure do not cause duplicate execution. Queue RFC (qRFC) is the same mechanism with an additional named queue that serialises execution order on the SAP side.

tRFC lifecycle

import saprfclib

conn = saprfclib.connect(
    ashost="sap-host",
    sysnr=0,
    client="100",
    user="RFC_USER",
    passwd="secret",
)

# Step 1: generate a unique 24-character TID.
tid = conn.create_tid()
print(f"TID: {tid}")           # e.g. "A3F1B2C4D5E6F7A8B9C0D1E2"

try:
    # Step 2: submit the call as tRFC.  The TID is embedded in the wire frame.
    conn.call_transactional(
        "STFC_CONNECTION",
        tid=tid,
        REQUTEXT="transactional call",
    )

    # Step 3: confirm the TID ONLY after verifying the submit succeeded.
    # Confirmation removes the TID from the SAP dedup table (ARFCSSTATE).
    conn.confirm_tid(tid)
    print(f"TID {tid} confirmed — exactly-once delivery guaranteed")

except saprfclib.CommunicationError as exc:
    # If the network fails during submit, do NOT confirm.
    # The TID remains valid for a retry; SAP dedup protects against duplicates.
    print(f"Submit failed — TID {tid} NOT confirmed; safe to retry: {exc}")

finally:
    conn.close()

qRFC variant

Pass a queue keyword argument to submit to a named inbound queue. SAP processes queued calls in FIFO order within each queue name (transaction SMQ2).

import saprfclib

conn = saprfclib.connect(
    ashost="sap-host",
    sysnr=0,
    client="100",
    user="RFC_USER",
    passwd="secret",
)

qtid = conn.create_tid()

try:
    # queue="MY_QUEUE" makes this a qRFC instead of a plain tRFC.
    conn.call_transactional(
        "STFC_CONNECTION",
        tid=qtid,
        queue="MY_QUEUE",          # Non-None queue name → queued RFC (qRFC)
        REQUTEXT="queued call",
    )
    conn.confirm_tid(qtid)
    print(f"qRFC submitted to queue MY_QUEUE, TID {qtid} confirmed")

except saprfclib.CommunicationError as exc:
    print(f"qRFC submit failed — do NOT confirm: {exc}")

finally:
    conn.close()

Summary of the lifecycle

Step	API call	When
1. Generate TID	tid = conn.create_tid()	Before every tRFC submit
2. Submit	conn.call_transactional(..., tid=tid)	Once per TID
3. Confirm	conn.confirm_tid(tid)	Only after successful submit
Retry	Re-use the same tid and call call_transactional again	On CommunicationError only

Do not confirm the TID if call_transactional raises CommunicationError — the same TID is safe to resubmit and SAP will deduplicate.