Troubleshooting Oracle XStream CDC Source Connector for Confluent Cloud

This section contains troubleshooting information for Oracle XStream CDC Source connector for Confluent Cloud.

Connector diagnostics script

The Confluent Oracle XStream CDC connector diagnostics script, orclcdc_diag.sql is a read-only script that collects key diagnostic information about the Oracle database and XStream configuration. This script helps troubleshoot connector issues and is provided solely for diagnostic purposes. The script output is an HTML report that you can upload to Confluent Support for further analysis.

This script does not collect or process any message content.

Prerequisites

  • Oracle Database version 19c and later.

  • Oracle database user with SYSDBA privileges.

  • Access to SQL*Plus command-line utility for running the script.

Usage instructions

Run the script

  • Connect to the Oracle database as a user with SYSDBA privileges. Note that if you are using a Container Database (CDB), you must connect to the root container.

  • Run the script using sqlplus. The script generates a diagnostic HTML report.

Upload the report

After you generate the report, you must upload it securely to Confluent.

  • Go to Secure File Transfer site. This site enables file encryption and tracks who accesses the files.

  • Upload the report.

Warning

Do not upload sensitive information to Confluent.

For more information, see Required Access to Confluent Network Sites.

Oracle XStream Out process hang during LOB processing

Problem

The Oracle XStream Out process can hang indefinitely when processing Large Objects (LOBs) data, especially during high ingestion rates with frequent LOB changes. The Apply Reader enters a Waiting for memory state, data streaming halts completely, and the process does not recover automatically.

Affected versions

This issue can occur on Oracle Database versions Oracle 19c and Oracle 21c when processing large LOB data.

Confirmed affected versions:

  • Oracle 19c: Oracle 19.30.0, 19.29.0, 19.28.0, 19.27.0, 19.26.0, 19.25.0, 19.22.0, 19.18.0, 19.11.0

  • Oracle 21c: Oracle 21.20.0

Other intermediate versions may also be affected.

Symptoms

  • XStream Out process (outbound server) stalls with no records flowing to the connector.

  • Apply Reader process shows state Waiting for memory in V$PROPAGATION_RECEIVER.

  • Heap analysis shows continued growth of knalf:txn_cnk allocations over time, indicating a memory leak in the XStream Out process.

Solution

  1. Apply Oracle patch 38090903 to resolve the memory leak.

  2. If the issue persists after applying the patch, tune the STREAMS_POOL_SIZE parameter to accommodate your LOB processing requirements. For more information, see Configure Streams pool size.

For further help, run the connector diagnostics script and contact Confluent Support with the diagnostic report.