User`s guide

OW TO USE YOUR PALMTOP
Through the Looking Glass: Fixing
and
Speeding Up Database Files
What to do when you get "Record Not Found" or "Cannot Open File"
error messages with any of the palmtop's built-in database applications
(ApptBook,
Database, PhoneBook, NoteTaker and WorldTime).
By Ed Keefe
I
t's been said before, but it bears
repeating : the database applica-
tions make the HP 100j200LX
unique among all its competition.
Not only does the palmtop's data-
base engine let you keep track of
phone numbers, notes, appoint-
ments, and To Do items, it also pro-
vides information
on the times and
phone prefixes in 450 cities. It even
lets you create custom, record-
keeping applications to suit your
particular needs or interests.
One of the greatest strengths of
the palmtop's database engine is
that each application can hold an
excessively large number of entries.
Some users have
reported that they
keep
thousands of phone numbers
in their palmtop. Others have cre-
ated custom databases with 1,500
records or more . The database fil~
sizes are often in the neighborhood
of 1 Megabyte.
How can the palmtop work
with database files that exceed the
working memory of the computer?
It
does so by using a "trick." The
database engine creates
an index of
all
the records in a database and
attaches this index to the informa-
tion file. It's like writing a reference
manual and attaching an index to
it.
When you start a database appli-
cation, the engine extracts the
index from the database file and
puts the index alone in working
memory . This index serves as the
raw material for the list view that
appears on the screen. When you
highlight one of the records in the
list and press (Enter), the engine
reaches out to the RAM disk and
copies that record into working
memory so you can view it or
modify it.
When you add, modify, or
delete a record, several things hap-
pen in the background: the record
is
stored on disk (or deleted from
the disk). Then the index is
updat-
ed and the database file is resized
to make it as small as possible.
Some people compare this resizing
to
defragmenting a hard-disk or
packing a database file. "Packing"
is a term that is familiar to dBASE
users.
On the palmtop, this resizing
or packing happens on-the-fly as
you work with a database. It
ensures that your information is
ABOUT THE AUTHOR
up-to-the-minute and safe. The
drawback is that, if you have a
large database, resizing and rein-
dexing can take a long time.
When you close a database
application, the index is reattached
to the information file
and the pro-
gram shuts down gracefully.
Everything has been designed to
work flawlessly and reliably, but,
on rare occasions, things can go
wrong. For instance, a portion of
your PC card might go bad for
some inexplicable reason, thereby
messing up several records in a
database file. Your
palmtop might
decide to lock up while it's trying
to resize or close a file. You
won't
know that something went wrong
until the next time you try to load
the database file. Then you'll get
an
error message telling you that a
record can't be found, or, worse
yet, the database can't be loaded.
Don't panic. This has hap-
pened to palmtop users before.
A long time contributor to Hewlett-Packard Handheld
support publications, Ed Keefe is an author, editor, pro-
grammer, computer
sci~nce instructor, and part-time con-
sultant in the computer
industry . Ed's articles appear in
The HP Palmtop Paper. He is also the editor of the book PC
In Your Pocket: Information When You Need It. Ed can be
reached at:
[e-mail]
THE HP PALMTOP PAPER SEPTEMBER/ OCTOBER 1997 11