Guralp Systems CD1.1 - Manual (Page 45)

Operator's Guide
8 Frame database files
The CD1.1 multiplexor stores subframes on disk in a simple
database file, indexed by time. One database file is created
per day.
By default, these database files are stored under /var/lib, but
some CMG-EAM modules have additional flash storage
mounted under /media/flash_module, so it may be
advantageous (where extra capacity is required) to reconfigure
the multiplexor to store its database files in a subdirectory in
this location (see the Database directory field in Section
4.2.1 on page 22 and Section 13, “Optional flash memory” on
page 79).
The first section of the database file contains 8640 pointers
(one for each possible frame start time within a 24-hour
period), which allows the multiplexor to quickly jump to the first
subframe received for a given time-stamp.
When new subframes are received, they are stored into the
database file, creating a new one if necessary. When the data
frame transmission period timer expires, all subframes for a
given time-stamp are read back from the database file and
transmitted to each connected output module. In addition, any
output module can request all subframes for a given time-
stamp, which allows the implementation of back-fill.
8.1 Managing database files
If left unattended, the database files will continue to grow as
subframes are received until the system runs out of secondary
storage (flash or hard disk space).
Files are named by ordinal day (YYYY-DDD in ISO8601
notation).
The files can either be manually managed, or an automatic task
to periodically prune old files can be created. To do this, in the
web interface, select “Configuration -> Tasks” from the left-
hand menu or from the command line, run
gconfig
and select “Routine tasks”.
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