Troubleshooting data tasks
This section describes problems that can occur when working with data tasks and how to troubleshoot.
Troubleshooting environmental errors
When a data task encounters an environmental error, for example, timeouts, network errors, or connection error, the data task will retry the operation automatically. If the error is not resolved after retrying, the data task stops running, and shows the status Error with an error message.
Landing tasks with data sources that are only accessible via Qlik Data Gateway - Data Movement:
The operation is retried an infinite number of times, with an interval of 5 seconds.
If the outage is long, the interval is doubled until an interval of 1800 seconds is reached.
Landing tasks with data sources that are accessible without Qlik Data Gateway - Data Movement, Storage tasks, Transform tasks and Data mart tasks:
The operation is retried 3 times, with an interval of 1 second.
Do the following:
Resolve the error using the error message.
Reload or resume operation of the data task.
Troubleshooting issues with a specific table
When a data task encounters an error while writing to a specific table, the data task will continue running. The table in error will show the status Error with an error message.
Resolve the error using the error message.
Reload the table that was in error.
NULL values in primary key columns
You may receive an error message when executing a data task: Unknown execution error - NULL result in a non-nullable column.
Columns used as a primary key must not contain NULL values, and should be non-nullable.
In the source data task, add an expression that converts all NULL values to a value, for example, 0.
You can also select another column to use as primary key.
Casting error when using Redshift as data platform
You may get the following error or similar when using Redshift as data platform: Failed to find conversion function from “unknown” to character varying
Missing casting of a constant expression. This may happen more frequently in data marts due to the higher complexity of the final query .
Cast the constant expression as text.
Troubleshooting a data task based on Data Gateway - Data Movement
You can get information about landing operation for data tasks based on Data Gateway - Data Movement by inspecting log files. You can also set the level of logging. Logs are available when the data task has completed its first run. You need one of the following permissions on the data task to view logs:
Viewing log files
Open the log viewer by clicking View logs in a landing data task based on Data Gateway - Data Movement. You can select which log file to view under Replication engine logs. You can scroll to the top and the bottom of the file with and .
Setting logging options
You can set the level of logging for different operations of the replication under Logging options.
You can set the following levels:
Show error messages.
Show informational messages.
Show additional information for troubleshooting purposes.
5. Detailed debug
Show detailed information for troubleshooting purposes.
The higher levels always include the messages from the lower levels. Therefore, if you select Error, only error messages are written to the log. However, if you select Info, informational messages, warnings, and error messages are included. In general, using the levels Debug and Detailed debug may generate large amounts of log data.
You can use Global to set the same level for all operations, or set the level individually for each operation.
Source - full load
Logs activity related to full load operations in the data source. This includes the SELECT statements executed against the source tables prior to full load.
Source - CDC
Logs activity related to CDC operations in the data source.Warning noteSetting this to Detailed debug level will generate very large amounts of data to the log.
Source – data
Detailed logging of data source activity related to full load and CDC operations.
Target - full load
Logs activity related to full load operations on the target.
Target - CDC
Logs activity related to CDC operations on the target.
Target – upload
Logs activity when files are transferred to the target.
Detailed logging of CDC activity, such as synchronization and storage of transactions.
Logs latency values for source and target.
Logs activity related to reading metadata, as well as metadata changes. Status of the replication task is also logged.
Logs infrastructure information, file system operations, and task management.
Logs information related to transformations that are performed.
Downloading diagnostic files
You can download a diagnostic package, task logs, and a memory report to assist you when troubleshooting the replication task associated with the landing task. You can only download one item at a time.
In the log viewer, click Download to expand.
Select the item to download.
The file will either be downloaded to your computer or you will be prompted to save it, depending on your browser settings.