| The FOCUS query command "? FDT" will give you physical info. about your FOCUS
file. The LENGTH column shows the size (in 4 character words) of each segment
in your file (including any FOCUS internal pointers). Divide this number into
993 and round down to get the number of segment instances which will fit on
each FOCUS page. Then multiply this number by the anticipated number of
instances of each segment (not necessarily the same as the # of input records)
and round up to get the number of FOCUS pages needed for your data.
Next calculate the pages needed for indexes. For each index field in your file,
add to the length of the index field 8 chars. for an index pointer. Multiply
this number by the # of instances for the segment and divide by 4096 (the size
of a FOCUS page). Round this number up and add to the data size from above.
This final number gives the required size in FOCUS pages. On VMS there are 4
disk blocks per FOCUS page, so multiply by 4 and you will have a ballpark
number to use when you go shopping for a disk.
Alternatively, you could contact IBI or the FUSE user group to see if anyone
else has the D&B data loaded into FOCUS and get an idea of disk requirements
from them. I'd try FUSE first, IBI tends to be protective of their clients'
confidentiality.
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| There is a way to calculate space usage using a FOCUS utility called
CALCFILE. What you need to use CALCFILE is a Master File Description
for the FOCUS database which will receive the data. If you had such
a Master File Description, or Master, written, you would invoke
FOCUS, and at the prompt, >, type EX CALCFILE. FOCUS then looks
for the master in your default directory. It then prompts you for
the NUMBER OF INSTANCES of each segment of the database. NOTE: FOCUS
is asking for the TOTAL number of instances of each segment which
you expect to store, NOT the number of child instances PER root
(or parent) instance.
The calculations it does are pretty simple-minded, and the utility
program itself has limitations. (Take a look at CALCFILE.FEX in
the IBI$FOCUS directory.) All of the calculations use INTEGER work
fields, which are limited to 9 positions, so for a database of the
size you are describing, you may find that some of the answers on
the report have overflowed the 9 positions. In that case, you can
divide the expected size in half and then multiply all of the answers
by 2, or you can copy the CALCFILE program and change all of the
work fields to 15-position packed fields.
The answers will be in the form of "Number of 4K FOCUS pages" and
"Number of VMS Blocks". Any further disk-specific size breakdowns
you will have to do yourself based on these numbers.
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