Data Buffering
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BLACK BOX
®
Advanced Console Server
Linear vs. Circular Buffering
For local data buffering, this parameter allow users to buffer data in either a circular or linear
fashion. Circular format (cir) is a revolving buffer file that is overwritten whenever the limit of
the buffer size (set by all.data_buffering) is reached. In linear format (lin), data transmission
between the remote device and the serial port ceases once the 4k bytes Rx buffer in the ker-
nel is reached. Then if a session is established to the serial port, the data in the buffer is
shown (dont_show_DBmenu must be 2), cleared, and data transmission is resumed. Linear
buffering is impossible if flow control is set to none. Default is cir.
Parameters Involved and Passed Values
Data Buffering uses the following parameters:
all.data_buffering
A non zero value activates data buffering (local or remote,
according to what was configured in the parameter
conf.nfs_data_buffering). If local data buffering, a file is
created on the BLACK BOX
®
Advanced Console Server; if
remote, a file is created through NFS in a remote server. All
data received from the port is captured in this file. If local
data buffering, this parameter means the maximum file
size (in bytes). If remote, this parameter is just a flag to
activate (greater than zero) or deactivate data buffering.
When local data buffering is used, each time the maximum
is reached the oldest 10% of stored data is discarded,
releasing space for new data (FIFO system) - circular file.
When remote data
all.data_buffering (cont.)
buffering is used, there's no maximum file size other than
the one imposed by the remote server - linear file. This file
can be viewed using the normal UNIX tools (cat, vi, more,
etc.).
Size is in bytes not kilobytes.
