.. efun:: void configure_driver(int what, mixed data)
  :include: <configuration.h>

  This efun configures runtime adjustable bahviour of the driver.

  Sets the option :arg:`what` to the value :arg:`data`.

  This function always causes the privilege_violation ("configure_driver", this_object(), what, data).

  .. todo:: above re: privilege violations, below re: should these be the macro definitions, or should those be elsewhere?

  :arg:`what` == :macro:`DC_MEMORY_LIMIT`
    Set new soft and hard memory limits for the driver. :arg:`data` is expected to be an array with two elements, which have to be integers giving the amount of memory in bytes. ``({<soft memory limit>, <hard memory limit>})``

  :arg:`what` == :macro:`DC_ENABLE_HEART_BEATS`
    Globally enable the calling of Heartbeats, if :arg:`data` is 1, globally disable them if :arg:`data` is 0. If called during heartbeat processing, the change comes into effect at the next backend cycle.

  :arg:`what` == :macro:`DC_LONG_EXEC_TIME`
    Set the time considered as (too) long for top-level executions. If an execution exceeds this time, a stack trace will be written to the debug log. The execution will continue at that point. :arg:`data` is an integer and measured in microseconds. A time of 0 disables the detection of long executions.

  :arg:`what` == :macro:`DC_DATA_CLEAN_TIME`
    Sets the average time between clean-ups of an objects data structures. This is not to be confused with the standard cleanup time which determines when :hook:`H_CLEAN_UP` is called. A long time for data cleanup may lead to larger memory consumption and prevents destructed objects being cleaned up. A too short time may lead to high loads and lag on the machine. The actual time delay will be a time between ``0.9*DC_DATA_CLEAN_TIME`` and ``1.1*DC_DATA_CLEAN_TIME``. Default at driver startup are 3600s. :arg:`data` is an integer and measured in seconds.

  :arg:`what` == :macro:`DC_TLS_CERTIFICATE`
    Sets the current certificate used for new TLS sessions. It can be one of the certificates in the key directory (command line option --tls-keydirectory) or the main certificate (given with --tls-certfile). Default is the main certificate or else the first certificate found in the directory. The chosen certificate at the time of the :efun:`tls_init_connection` call is used for that connection. :arg:`data` is a string containing the SHA1 fingerprint of the certificate with hexadecimal numbers, it may contain colons or whitespaces (for example ``5A:FE:CA:57:1E:50:5E:1E:C7:ED:BA:11:AD:50:10:75:0F:7A:1E:50``). When loading certificates their fingerprints are printed on stdout and into the logfile.

  :history 3.3.719 introduced:
  :history 3.5.0 changed: added :macro:`DC_ENABLE_HEART_BEATS`, :macro:`DC_LONG_EXEC_TIME`, :macro:`DC_DATA_CLEAN_TIME`, :macro:`DC_TLS_CERTIFICATE` was added in 3.5.0.

  .. seealso:: :efun:`configure_interactive`