Log files for q processes running on Kx Control, including log files for Kx Control itself and any daemons, are stored in a directory configured in delta.profile. The path to this directory is stored as the environment variable FD_LOGDIR and is derived from the environment variable DELTADATA_HOME:

$ export FD_LOGDIR=${DELTADATA_HOME}/DeltaControlData/logdir

The log file for Kx Control is DeltaControl.log and for the daemon is DeltaControlDaemon.log. Other processes running on Kx Control have their log-file names and other logging details configured in the configuration parameter DC_LOGGING:DEFAULT and its overrides. Overrides of DC_LOGGING named after the process instances to which they apply. The parameter attributes of DC_LOGGING are:


Logging APIs

API documentation is available for the logging APIs.


The above link discusses logging using components. This can be useful for toggling debug level on a per-component level. This means debug messages are available without flooding the log files. Components can be enabled or explicitly disabled using instance parameters; .log.cmp.debugEnabled and .log.cmp.debugDisabled.

Instance parameters

Log file name configuration

The naming convention of log files for processes running on the Control platform is configured inDC_LOGGING, as the logFile attribute. The log file name can contain temporal values which are indicated with codes.

code value
%Y year
%m month
%d day
%H hour
%M minute
%S second
%U millisecond
%N nanosecond


Log precision and console width

The number of decimal places for the time of logged messages is set using the logPrecision attribute.

The consoleWidth attribute is analogous to the console size of a q session, and is used to control the maximum number of rows and columns for output.

Log file rolling

Log files can be configured to roll. Rolling creates a file containing the current contents of the log file and sets the log file to be empty. Log file rolling is also configured via DC_LOGGING and its overrides.

datePattern : Appended to the log file name to create the new file when rolling and can contain the same temporal values as logFile

rollMode : When rolling occurs:

-   `size`: the log file will roll when it reaches the value of the `rollSize` attribute in megabyte
-   `daily`: the log file will be rolled at the time configured as `rollTime`.

rollBy : Either - process: each process rolls its own log file - DeltaControl: Kx Control itself will roll the log files

On Windows DeltaControl mode isn’t supported

Publishing log messages

It is possible to publish logged-out, warning and error messages, as well as to query the log and access log messages when they occur on a process. In DC_LOGGING the publishInitAnalytic is the analytic called at start-up to enable this functionality. The analytic publishAnalytic publishes the log messages to any process configured in consumerProcesses.

Which messages are published can be configured in DC_LOG_PUBLISH:DEFAULT. Additional rows of this parameter can be added to have different behavior for different process instances. The parameter attributes of DC_LOG_PUBLISH are:


If out, warn or err are true then out, warn and err log messages respectively are published as dxLog messages to the consumer processes defined in DC_LOGGING.

If the replay column is true then once a connection between a process and the consumer process is made, old log messages from the log file will be published to the consumer process.

The querylog column configures publishing from .pm.querylog. If true, two dxLog messages are published: one when the query is received by the process, and one after the query has executed.

If the accesslog column is true then a .pm.accesslog message is published when a connection attempt is made to the process.