That was it. The connection tracker on the database server’s firewall was overflowing—not from real connections, but from a half-open state that never resolved. An old kernel bug, triggered by a specific jdbc driver version. The driver would send a cancelation signal, the firewall would hold a ghost entry, and after 60,000 ghosts, the table would drop legitimate SYN packets before they ever reached the database process .
: Work with your network team to open the required port in both directions.
Security and compliance considerations
jdbc:postgresql://host:5432/database?connectTimeout=30&socketTimeout=60
Preventive measures
Download the supported JDBC driver directly from your database vendor (e.g., mssql-jdbc.jar or db2jcc4.jar ).
The query engine fails to initialize if the Cognos data source configuration routes requests to an incorrect destination port. A frequent mistake involves enforcing Secure Sockets Layer (SSL) encryption in the connection string parameters while keeping the traffic routed through standard non-encrypted ports (e.g., trying to run SSL traffic over standard SQL Server port 1433 instead of an encrypted port). 3. Client and System Locale Mismatches That was it
Before jumping into fixes, let’s outline the typical scenarios that trigger the xqe-jdb-0001 error. Understanding these causes will help you narrow down your troubleshooting steps.
: If the UI message is vague, detailed error stacks are recorded in the The driver would send a cancelation signal, the
