SAP Production Incident – Troubleshooting SAP Router, APP Dispatcher, and HANA Dependency Failure Introduction Recently I handled an SAP Production incident where users were suddenly unable to access critical SAP production services including SAP GUI At first glance the issue looked like a network or firewall problem because users received a connection refused error when trying to connect to the SAP environment. However, after tracing the entire SAP landscape step-by-step, the actual issue turned out to be a startup dependency problem involving: SAP Router SAP Application Dispatcher SAP HANA Database Web Dispatcher backend connectivity This article shares the troubleshooting process from infrastructure level until application recovery. Note: Hostnames, IP addresses, SID names, and environment details have been anonymized for confidentiality. Environment Overview The SAP production landscape consisted of several separate virtual machines: 1. SAP Router VM 2. SAP Application VM 3. SAP Web Dispatcher VM 4. SAP Database VM Architecture flow: Client ↓ SAP Router ↓ SAP APP Dispatcher ↓ SAP HANA Database Initial Symptoms Users reported: SAP GUI connection failed web application inaccessible SAP GUI error: partner ':3230' not reached Connection refused At this stage there were several possible causes: Firewall issue NAT issue SAP Router down Dispatcher down Database issue SAP service startup failure Step 1 – Validate Network Connectivity Initial external validation was performed using: nmap -Pn -sT -sV \ -p 3299 ,3230,3330,50013,50014 Result: 3299 closed 3230 closed 50013 open 50014 open Interesting finding: SAPControl ports were alive but SAP application ports were closed. This usually means: sapstartsrv running but SAP application services not operational Step 2 – SAP Router Investigation SAP Router port: 3299 was confirmed not listening. Further inspection on the SAP Router VM revealed that SAP Router was started manually using: ./saprouter -r -s 3299 ... It was not configured as a proper persistent service. Additional discovery: The startup script previously used an incorrect parameter: -S 3299 instead of: -s 3299 After correcting and starting the service manually: ./saprouter -r -s 3299 ... Result: 3299 LISTEN SAP Router connectivity was restored successfully. Step 3 – SAP APP Instance Investigation Next, SAP instance status was checked: sapcontrol -nr 30 -function GetProcessList sapcontrol -nr 31 -function GetProcessList Initial status: Instance 31 msg_server GRAY enq_server GRAY Instance 30 disp+work GRAY gateway stopped Port validation: 3230 CLOSED This explained the SAP GUI connection refusal. Step 4 – Recover SAP Central Services Instance 31 was started first: sapcontrol -nr 31 -function StartSystem Result: msg_server GREEN enq_server GREEN However, instance 30 still failed to become healthy. Step 5 – Dispatcher Failure Analysis Dispatcher logs were analyzed: cd /usr/sap//D30/work Important logs: dev_disp sapstart.log Critical error found: DpWpCheck: no more work processes Multiple work processes terminated unexpectedly. At this point the investigation shifted toward database dependency. Step 6 – HANA Database Investigation HANA status check: HDB info Result: HANA services not fully running Important HANA services such as: nameserver indexserver xsengine were unavailable. This explained why: SAP APP work processes failed during startup. The SAP dispatcher depended on HANA connectivity. Step 7 – Start HANA Database Database services were started manually: HDB start After startup: HANA processes became active Ports became available again. Step 8 – Recover SAP APP Instance After HANA became healthy: sapcontrol -nr 30 -function StartSystem Result: disp+work GREEN gwrd GREEN icman GREEN Port validation: 3230 LISTEN SAP GUI connectivity was restored. Step 9 – Verify Web Dispatcher Web Dispatcher status: sapcontrol -nr 00 -function GetProcessList Initially: YELLOW Later: GREEN Backend connectivity recovered automatically after APP and HANA services became available. Web application login page became accessible again. Root Cause Analysis The incident was ultimately caused by: Several SAP services did not auto-start properly after system startup/reboot. Affected components: SAP Router service SAP HANA Database services SAP APP dispatcher dependency chain Impact chain: HANA DB not running ↓ SAP APP work processes failed ↓ Dispatcher shutdown ↓ Port 3230 unavailable ↓ SAP GUI connection refused ↓ Web Dispatcher backend degraded Key Lessons Learned 1. Open SAPControl Port Does Not Mean SAP Is Healthy Ports like: 50013 50014 may still be reachable even when SAP applications are completely down. Because: sapstartsrv can remain alive independently. 2. SAP Startup Dependency Order Matters Correct startup sequence: 1. HANA Database 2. ASCS / Message Server 3. APP Dispatcher 4. Web Dispatcher 5. SAP Router If APP starts before HANA: work processes may terminate immediately. 3. SAP Router Should Use Proper Service Management Running SAP Router manually from shell sessions is risky. Better approach: systemd service persistent startup automatic recovery 4. Dispatcher Logs Are Extremely Important The key clue came from: dev_disp which clearly showed: all work processes terminated without that log analysis, troubleshooting could easily remain focused on networking instead of backend dependencies. Final Status All SAP services recovered successfully: [OK] SAP Router running [OK] HANA running [OK] SAP APP healthy [OK] Dispatcher GREEN [OK] Web Dispatcher GREEN [OK] SAP GUI accessible [OK] Web application accessible Conclusion This incident demonstrated how SAP outages can initially look like simple network issues while the real root cause actually exists deep in service dependency chains. The troubleshooting flow that worked best was: Network → SAP Router → SAP Instance → Dispatcher Logs → HANA Dependency → Service Recovery In complex SAP environments, understanding the startup relationship between routing services, application dispatcher services, web dispatcher services, and backend databases is critical for fast recovery and accurate root cause analysis.