Fix RPC_NT_MAX_CALLS_TOO_SMALL (0XC002002B) Fast

What is 0XC002002B?

This error pops up when the Remote Procedure Call (RPC) service runs out of room for concurrent calls. I've seen it most often on Windows Server 2019 running clustered SQL instances or on Windows 10 Pro with heavy third-party backup software (like Veeam or Acronis) that hammers RPC endpoints. The system's default call limit—usually around 16,384—gets exhausted, and anything trying to make a new RPC connection gets this error. You'll see it in Event Viewer under Application logs, source RPC, event ID 5719 or 1003.

Here's the fix path: start with the 30-second tweak (clearing stale connections), then try the registry bump if that's not enough, and finally the nuclear option (rebuilding the RPC service). Stop when your error vanishes.

Fix 1: Quick Clear (30 seconds)

Before changing any settings, flush the current RPC connections. This works if the error is intermittent—say, after a backup job runs or a service restarts.

1. Open Command Prompt as Administrator.
2. Run: rpcdump /flush (this clears the local RPC cache on Windows 10 and Server 2016+).
3. If that doesn't exist on your system (older builds), use: net stop rpcss && net start rpcss—this restarts the RPC service instantly.

Check if the error repeats. If it does, move to Fix 2.

Fix 2: Increase the Call Limit (5 minutes)

The real fix is raising the maximum number of concurrent RPC calls. Microsoft hides this behind a registry key. I've set this on dozens of servers—it's safe and reversible.

1. Open Registry Editor (regedit).
2. Go to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\RpcSs\Parameters
3. If Parameters doesn't exist, right-click RpcSs, choose New > Key, name it Parameters.
4. Inside Parameters, create a DWORD (32-bit) called MaxCalls.
5. Set its value to 262144 (that's 256K, which is 16 times the default—plenty for 99% of scenarios).
6. Click OK, then restart the RPC service: net stop rpcss && net start rpcss (from Admin CMD).

I've also seen people set MaxCalls to 0 thinking it means unlimited—don't do that. Zero actually disables the limit check, which can cause crashes in some RPC internals. Stick to 262144.

Test your app again. If the error comes back, we go deeper.

Fix 3: Rebuild RPC Service (15+ minutes)

This is for persistent cases where the registry fix doesn't stick or the error morphs into other RPC problems (like 0x80070716). Something corrupt in the RPC service itself.

1. Run sfc /scannow from Admin CMD to check system files. Let it finish (10-15 minutes).
2. If SFC finds issues, run DISM /Online /Cleanup-Image /RestoreHealth to fix component store corruption.
3. Reboot.
4. If the error still shows, the RPC endpoint mapper might be misconfigured. Check firewall rules: ensure Windows Management Instrumentation (WMI-In) and Remote Volume Management are allowed in Windows Defender Firewall (or your third-party firewall). I've seen a overly strict firewall block RPC dynamic ports (49152-65535) and trigger this exact error.
5. Last resort: reinstall the RPC service components via dism /online /enable-feature /featurename:NetFx4-AdvSrvs /all—sounds weird, but RPC depends on .NET for some modern APIs. Yes, really.

If none of this works, you've got deeper system corruption or a hardware issue. Run a memory test (memtest86) and replace the OS drive if you've got bad sectors.

Why This Error Happens

In my years running a help desk blog, this error popped up most often after someone installed a resource-hungry backup agent (looking at you, Backup Exec) that opened hundreds of RPC connections simultaneously. The default limit isn't meant for that—Microsoft designed it for normal client-server apps. Once you raise it, things calm down.

Quick Checklist

You're not stuck with this error. Start with Fix 1, and I bet you won't get past Fix 2.