RFC, CPI-C & Network Connectivity

An RFC destination left with no logon credentials tests fine interactively but breaks the moment a background job uses it. Why?

You need to add RFC/gateway capacity to a landscape but the host has no spare resources for dialog work processes. What kind of instance can you install, and what does it deliberately lack?

For an HTTP RFC destination, single sign-on with the same SAP user and trusted-RFC logon are offered for one connection type but not the other. Which type gets them, and why?

Unlike tRFC/qRFC where the source system pushes data to the target, how does the Local Data Queue (LDQ) deliver data, and what scenario is it built for?

You need to protect the network links between SAP system components with your organization's own security product rather than SAP's built-in mechanisms. Which interface makes that possible?

A WAN link works fine between the SAP GUI frontends and the application servers, so the team wants to stretch the same WAN between the application server and the database server. Why is that a mistake?

A parallel-processing job (like a large client copy) is hammering one dialog instance with RFCs while other instances sit idle. What mechanism spreads that RFC load, and how is it invoked in code?

Asynchronous RFCs are silently failing to execute even though the destination tests fine in SM59. Which transaction diagnoses whether the cause is a resource shortage, not a connection problem?

In SARFC, an instance shows fewer usable RFC resources than it has dialog work processes even when the system is quiet. What reserves that gap?

You raise an RFC quota parameter in RZ12, the RFC failures stop, everyone moves on — then after the next instance restart the same failures return. What did you skip?

You want to lock down who may create and change RFC destinations, but restricting who may call function modules over RFC didn't help. Which authorization object governs administering connections, and by what fields?

Someone created an SM59 destination with a typo in its name and wants to just rename it in place. Why can't they, and what's the planning consequence?

Before relying on a new SAP-to-SAP RFC destination, why should you run the Unicode Test on the Unicode tab, and what does it actually decide?

An intermittent RFC interface is misbehaving and you need to see exactly what every call on that one destination is doing. What do you enable, and where do you read the result?

The SM59 Connection Test comes back green, yet the interface still fails with a logon error in production. Why is a passing connection test not reassuring here?

For a type-T destination to an external RFC server program, when do you supply a host name and program path versus only a program ID?

A registered external RFC server program can wait at the gateway for requests from any SAP system that names it. What controls whether the gateway actually lets such programs register and start?

You must connect to a non-SAP external program over TCP/IP from SM59. Which connection type, and how do you avoid confusing it with the ABAP and HTTP types?

All RFC, CPI-C, and external-system (EDI/fax) traffic on one instance stops. A junior admin suspects 'too few gateway processes.' Why is that the wrong root cause, and where should you actually look?

You are writing an RFC call and must pick synchronous vs asynchronous (IN BACKGROUND TASK). Which property of the call decides it?

tRFC calls are being delivered but in the wrong sequence, corrupting dependent updates downstream. What does qRFC add that fixes this, and what drives tRFC retries in the first place?

An admin treats RFC and CPI-C as independent communication layers and chases two separate bugs when both fail at once. Given how CPI-C is implemented in SAP, why is that the wrong mental model?

You set SAP_IPv6_ACTIVE=1 on one instance to enable IPv6. Why can this still cause system-wide connectivity problems, and what is the procedural rule you skipped?

Which monitor transaction belongs to each RFC type (tRFC, qRFC inbound/outbound/registration, bgRFC, local data queue)?

You must send messages to a target system that is sometimes down, and they must arrive once and in the order they were created. Which RFC type fits, and why are sRFC and aRFC the wrong picks?

Before activating IPv6 for SAP communication on an older landscape, what release floor must you verify, and what legacy transport caveat still matters?

A developer assumes that once an SM59 destination from system A to B exists, B can use it to call back into A. Why is that wrong?

A trusted-system RFC destination needs no stored logon data. Why is choosing trusted RFC a security decision, not just a convenience one, and where is the trust maintained?

A system is moving to a new host and dozens of RFC destinations point at it. Why does a type-L design turn this into a one-line change, and what would force the painful per-destination edit instead?

A type-3 RFC destination to another SAP system suddenly fails to log on after a routine password rotation on the target. What design fact explains this, and what user type should have been used?