MDR-2000
V3
User's Reference Manual
Communications
CDR
for example) then the MDR-2000 may become full with image records and deleted
CDR
records even though the data collection process reveals that the buffer
is
empty
of
records.
Also in this case the residual deleted CDR records will still be reflected in the 'Number
of
Records
Stored' and 'Records to be Collected' fields
of
the SHOW STATUS command in the Interactive
Monitor. Therefore these fields remain accurate indicators
of
the storage utilized in the MDR-2000
but not necessarily true indicators
of
how many valid records remain.
4.4 Large Blocksize Polling
Polling records in blocksizes greater than one can significantly improve data transmission rates at
higher baud rates, but is more prone to errors since the blocks
of
data are larger. The larger blocks
means that
if
an error occurs the entire block must be retransmitted. Using this feature is usually
not necessary but has been included with the MDR-2000 for large installations, such as service
bureau operations, where the elapsed time for overnight data collection is sometimes a constraint.
The MDR-2000 must be configured to transmit data in blocksizes greater than 1 record per block.
This is done by using the SET XFER BLOCK command in the Interactive Monitor. Blocksizes
from 1 through 255 may be specified.
Two dedicated computer-to-computer commands are used to transmit large blocks
of
records.
These are the
'XB'
and
'RB'
commands which are both described in the section on 'Computer-to-
Computer Commands'. Using the Transfer Blocksize does not affect the used
of
the regular
computer-to-computer commands, '
XT'
and '
OK
',
used in downloading single record blocks.
The '
XB'
command
is
used
as
a replacement for the '
XT'
command
to
transmit a block ofrecords.
Each record in the block has a complete protocol as described in the section 'Polling' in this
manual. Successive
'XB'
command download successive blocks ofrecords, the
'OK'
command is
not used and there is no replacement for it when working with large blocks.
If
an error is detected in any
of
the records in a block then the entire block must be retransmitted.
Since the MDR-2000 has already indexed to the next block after the completion
of
the previous
'
XB'
command it is necessary
to
issue an 'RB' to reset the pointers to the previous block. Only one
'RB'
command can be used, they cannot be stacked to move backwards multiple blocks.
When the end
of
the recorded data has been reached a partial block may be transmitted. This will
be followed by one more block which contains the
'END
' record. The
'CL'
command should then
be used
to
erase the downloaded data from the MDR-2000 thereby freeing up the storage for new
data from the PBX.
4-8
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