SAP Data Migration Troubleshooting: Resolving 'Connection Refused', Timeouts, and Performance Bottlenecks

Understanding SAP Data Migration Failures

Executing an sap data migration—whether you are using the SAP S/4HANA Migration Cockpit (LTMC/Fiori), Legacy System Migration Workbench (LSMW), or SAP Data Services—places immense stress on the NetWeaver/ABAP stack and underlying HANA database. When moving millions of business partner, material master, or financial records, system limits are frequently tested, resulting in frustrating roadblocks.

This sap troubleshooting guide is designed for DevOps engineers, SAP Basis administrators, and migration leads to systematically diagnose and resolve the most common and critical migration disruptions.

Diagnosing the Core Symptoms

When a migration fails, the error usually manifests in one of four distinct ways. Recognizing the specific pattern is the first step in effective sap troubleshooting.

1. SAP Connection Refused (WSAECONNREFUSED / NiPConnect2): This network-layer error occurs when the SAP GUI, Migration Cockpit, or RFC destination cannot reach the SAP Dispatcher or Gateway. It indicates that the target port (typically 32NN for dispatcher or 33NN for gateway, where NN is the instance number) is unreachable.
2. SAP Timeout (TIME_OUT): Seen in transaction ST22 as an ABAP short dump. SAP restricts how long a foreground (Dialog) task can run. If a migration validation or upload exceeds this limit, the system forcibly terminates it.
3. SAP Slow Performance: Data loads that should take minutes stretch into hours. This is typically caused by database lock contention, missing indexes, or processing massive payloads sequentially instead of in parallel.
4. SAP Crash / Memory Dumps: Severe memory exhaustion (e.g., TSV_TNEW_PAGE_ALLOC_FAILED) where the SAP work process consumes all available heap and extended memory, causing the system to abort the transaction to protect overall system stability.

Step 1: Resolving 'SAP Connection Refused' Errors

The WSAECONNREFUSED or NiPConnect2: Connection refused error is a staple of network and configuration issues. If sap not working is reported during cross-system data transfer, investigate the network topology.

1. Verify Port Accessibility using Niping SAP provides a native tool called niping to test SAP network connectivity without the overhead of the application layer. Do not rely solely on ping. From your application server or migration tool host, execute a niping test to the target SAP Gateway: niping -c -H <Target_SAP_Host> -S 3300 (Replace 00 with your instance number). If this fails, you have a firewall issue, a VPN drop, or an inactive SAP Gateway.

2. Check SAP Gateway Status (SMGW) Log into the target system (if accessible via another route) and check transaction SMGW. Ensure the gateway process is running and hasn't exhausted its maximum number of connections (gw/max_conn). Check the developer traces (dev_rd) in transaction AL11 for gateway crash logs.

3. Validate RFC Destinations (SM59) During an sap configuration tutorial setup for migration, RFCs are often hastily configured. Go to transaction SM59. Perform a connection test and an authorization test. Ensure the target host IP is correctly mapped in the /etc/hosts file of the SAP application server or DNS, as SAP relies heavily on accurate host resolution.

Step 2: Fixing SAP Timeouts (TIME_OUT) Dumps

A sap timeout occurs when a dialog work process (DIA) exceeds the system parameter rdisp/max_wprun_time (default is usually 600 seconds / 10 minutes).

1. Move Heavy Loads to Background (BGD) The golden rule of SAP processing: never run heavy loads in the foreground. Background processes are not subject to rdisp/max_wprun_time. In LSMW, ensure you select 'Background' for the data read and convert steps. In the Migration Cockpit, jobs are automatically scheduled as background processes, but initial validations may timeout if the payload is too large.

2. Dynamically Adjust the Timeout Parameter If you absolutely must run a configuration or validation step in the foreground, you can temporarily increase the timeout threshold.

• Go to transaction RZ11.
• Enter parameter name: rdisp/max_wprun_time.
• Change the value from 600 to 3600 (1 hour). Note: This is a dynamic parameter, meaning it takes effect immediately without an SAP instance restart. Always revert this back post-migration to prevent runaway processes from hanging the system.

Step 3: Addressing SAP Slow Performance During Loads

If the data is flowing but sap slow performance is threatening your cutover window, you must identify the bottleneck. Is it CPU, Memory, Database, or Application logic?

1. Monitor Work Processes (SM50 / SM66) Open transaction SM50. Look at the background (BGD) processes handling the migration.

• Are they stuck in Sequential Read status? This indicates a database bottleneck (missing index or massive table scan).
• Are they stuck in Roll in or Hold status? This indicates memory exhaustion or RFC wait times.

2. Optimize API/BAPI Batch Sizes Sending 100,000 records in a single commit block is a recipe for disaster. It overwhelms the SAP Enqueue (Lock) server and creates massive database undo/redo logs. Reduce your commit batch size in the migration tool. The sweet spot for SAP APIs is usually between 100 and 1,000 records per commit, depending on the complexity of the business object (e.g., Material Master requires smaller batches than simple FI GL postings).

3. Parallelize the Migration Ensure your sap configuration utilizes multiple background processes. If you have 20 BGD processes available (check RZ04), configure the SAP S/4HANA Migration Cockpit to use a parallelization factor of 10-15. Leave some processes open for regular system operations to prevent locking out other administrators.

Step 4: Preventing the SAP Crash (Memory Dumps)

An unexpected sap crash or rollback during migration is typically tied to ABAP memory limitations. If you see TSV_TNEW_PAGE_ALLOC_FAILED in transaction ST22, the system ran out of Extended Memory (EM) or Heap Memory.

1. Tune Memory Parameters (RZ10) SAP uses a specific sequence of memory allocation (Roll -> Extended Memory -> Heap). For large migrations, the Extended Memory must be sufficient. Check and modify these parameters in RZ10 (requires an instance restart):

• ztta/roll_extension: Defines the maximum extended memory a single user session can allocate. Increase this if a single massive migration job is failing.
• em/initial_size_MB: Defines the total extended memory pool for the instance. Ensure this is adequately sized based on the physical RAM of the server (e.g., set to 70-80% of physical RAM on a dedicated app server).
• abap/heap_area_dia and abap/heap_area_nondia: Controls local heap allocation.

2. Check HANA Database Logs If the application server is fine, check the HANA database. Use SAP HANA Studio or DB02. Look for out-of-memory (OOM) trace files (indexserver_alert*.trc). A database crash will immediately sever the connection to the application server, presenting as an application crash.

Conclusion

Successful SAP data migration requires rigorous infrastructure preparation. Before initiating production cutover, ensure network ports are open, RFCs are stable, batch sizes are optimized, and system parameters like memory and timeouts are appropriately tuned for bulk data processing.