lttng-enable-rotation.1.txt: add that SIZE/PERIOD are approximations

[lttng-tools.git] / doc / man / lttng-enable-rotation.1.txt

lttng-enable-rotation(1)
========================


NAME
----
lttng-enable-rotation - Set a tracing session's rotation schedule


SYNOPSIS
--------
[verse]
*lttng* ['linkgenoptions:(GENERAL OPTIONS)'] *enable-rotation* (option:--timer='PERIOD' | option:--size='SIZE')
      [option:--session='SESSION']


DESCRIPTION
-----------
The `lttng enable-rotation` command sets a rotation schedule for the
current tracing session, or for the tracing session named 'SESSION' if
provided. See man:lttng-rotate(1) for more information about the
concepts of a tracing session _rotation_ and a _trace chunk_.

With the option:--timer option, the rotation schedule is set so that an
automatic rotation occurs at least every 'PERIOD' (microseconds without
a unit suffix).

With the option:--size option, the rotation schedule is set
so that an automatic rotation occurs every time the total size of the
flushed part of the current trace chunk is at least 'SIZE' (bytes
without a unit suffix).

For both option:--timer and option:--size options, LTTng checks the
schedule condition periodically using the monitor timers of the tracing
session's channels. This means that, with the option:--timer option, the
automatic rotation can occur when the elapsed time since the last
automatic rotation is greater than 'PERIOD', and with the option:--size
option, the automatic rotation can occur when the size of the flushed
part of the current trace chunk is greater than 'SIZE'. Therefore the
'PERIOD' and 'SIZE' arguments are approximations. See the
nloption:--monitor-timer option in man:lttng-enable-channel(1) for more
information about the monitor timer.

The naming convention of a trace chunk archive which an automatic
rotation creates is the same as with the immediate rotation command,
man:lttng-rotate(1).

You can unset a rotation schedule with the man:lttng-disable-rotation(1)
command.

See <<limitations,LIMITATIONS>> for important limitations regarding
this command.


include::common-cmd-options-head.txt[]


Rotation schedule condition
~~~~~~~~~~~~~~~~~~~~~~~~~~~
One of:

option:--size='SIZE'::
    Set a rotation schedule so that an automatic rotation occurs every
    time the total size of the flushed part of the current trace chunk
    is at least 'SIZE' bytes. The `k` (kiB), `M` (MiB), and `G` (GiB)
    suffixes are supported.

option:--timer='PERIOD'::
    Set a rotation schedule so that an automatic rotation occurs at
    least every 'PERIOD' microseconds. The `ms` (milliseconds), `s`
    (seconds), `m` (minutes), and `h` (hours) suffixes are supported.


Target
~~~~~~
option:-s 'SESSION', option:--session='SESSION'::
    Set a rotation schedule for the tracing session named 'SESSION'
    instead of the current tracing session.


include::common-cmd-help-options.txt[]


[[limitations]]
LIMITATIONS
-----------
The `lttng enable-rotation` command only works when:

* The tracing session is created in normal mode or in network streaming
  mode (see man:lttng-create(1)).

* No channel was created with a configured trace file count or size
  limit (see the nloption:--tracefile-size and
  nloption:--tracefile-count options in man:lttng-enable-channel(1)).

For a given tracing session, LTTng only performs an automatic rotation
when no other rotation is currently happening.


include::common-cmd-footer.txt[]


SEE ALSO
--------
man:lttng-rotate(1),
man:lttng-disable-rotation(1),
man:lttng(1)