Re: dbf trashing problem after upgrade

hi

i will do some testing with the commands you mentioned and let you know of
the result.
thanks

"Anders Altberg" <x_pragma@xxxxxxxxx> wrote in message
news:%23d0nm01OFHA.624@xxxxxxxxxxxxxxxxxxxxxxx
> Hi Anis
>> i always issue flush
>> commands at the end of every transaction to clean the buffers and
> everything
>> works perfectly well if the users exit the programs normally.
>
> FLUSH doesn't work on disks that have an active Write cache, which is
> common
> on Windows 2000 and XP an possibly other Windows versions. This feature
> can
> be turned off but may reappear when the computer reboots.
> Tha'ts why VFP in recent versions has added commands like SYS(1104) 'Purge
> cached memory' and FLUSH FORCE to overwride the Write cache feature of the
> OS.
>
> When you say 'transactions' are you talking of transactions in general as
> data modifications or as the BEGIN TRANSACTION - END TRANSACTION /
> ROLLBACK
> commands in VFP?
> -Anders
>
>
> "Anis" <anis@xxxxxxxxxx> wrote in message
> news:ucven0rOFHA.3880@xxxxxxxxxxxxxxxxxxxxxxx
>> thanks for your reply brett,
>>
>> the vfp version of the application uses almost the same code and the same
>> business rules as the old one. the only changes that have taken place
>> are
>> the platform (fpw26 to vfp7) and the os (98se to xp). i always issue
>> flush
>> commands at the end of every transaction to clean the buffers and
> everything
>> works perfectly well if the users exit the programs normally. i also set
>> refresh to 5,5 to periodically update the tables as i used to do in
>> fpw26.
>> my big problem is with recovery anytime a crash occurs (crash here being
>> that somebody turns off the central ups by mistake and all systems turn
> off
>> or even if the server crashes or restarts by mistake due to a user error)
>> previously (fpw26 with foxfix on win98 se), anytime any of this happened,
>> the application would automatically correct the files with foxfix and no
> bad
>> records (garbage) are appended to the file (the last transaction before
> the
>> flush usually gets lost). but now, with vfp7 running on xp, i always get
> the
>> garbage plus a lot of damaged records. could this be a problem with vfp7
> and
>> xp ? or possibly a problem with the way xp manages memory related to
> foxpro.
>> i have noticed that problems are less likely to occur on win2000 machines
>> but they do occur nonetheless.
>>
>> anis
>>
>>
>>
>> "Brett Wickard" <nospam-bullmoose-nospam@xxxxxxxxxxx> wrote in message
>> news:%23K%23BkgrOFHA.524@xxxxxxxxxxxxxxxxxxxxxxx
>> > Wow, that sounds like a frustrating problem. I also develop POS
> solutions
>> > and have had very, very good luck with database integrity. On the
>> > store
>> > level, the terminals share a DBF on the server. I would absolutely
>> > make
>> > sure the server is running an NT kernel based O/S (i.e. NT/2000/XP). I
>> > have had excellent results with NT kernel based, but 98 was so unstable
> as
>> > the file sharing server that we dumped it years ago. As for the POS
>> > terminals themselves, I do allow clients to have old O/S's running the
>> > software, and again, if the file server is running a good O/S and has a
>> > good UPS, corruption should almost never happen.
>> >
>> > If you give me a few more details about your topology/setup of your
> sites,
>> > I might be able to offer advice that will help. Or I'll rant about
>> > something that doesn't help and will just takeup bandwidth :)
>> >
>> >
>> > "Anis" <anis@xxxxxxxxxx> wrote in message
>> > news:%23t$fl5pOFHA.3000@xxxxxxxxxxxxxxxxxxxxxxx
>> >> greetings to all,
>> >>
>> >> we have been loyal foxpro users for 12 years now and have developed
>> >> various point-of-sale applications by using forpro 2.6
>> >> for windows. our pos applications run on windows 98 se and in most
> cases
>> >> run in a network environment with at least 3 users
>> >> and above. due to the nature of foxpro dbfs and the serious issue of
> dbf
>> >> files being trashed which especially occurs when the
>> >> ups system goes down unexpectedly or when the server (also a win98 se
>> >> machine) crashes, we extensivley used foxfix to remedy
>> >> any issue automaticallty from the software and things seemed to work
>> >> great 99.99% of the time all in all resulting in a very
>> >> stable and recoverable application that made our clients very happy
>> >> and
>> >> our support staff glad.
>> >>
>> >> last year, we converted one of our pos applications to vfp7 sp1
> (running
>> >> on windows xp) and since we were loyal foxfix users,
>> >> we purchased foxfix 5.2 in order to obtain and attain the reliablity
>> >> which we were accustomed to from the marriage of fpw26
>> >> and foxfix in our suite of applications. but things now seem to have
>> >> changed. any time a crash occurs - for example the ups
>> >> system goes down - foxfix is able to make all dbfs usable after a
>> >> total
>> >> system restart, but now opening any dbf file which is
>> >> updated extensivley by the application (the sales file for example)
>> >> and
>> >> setting the order to the primary index tag yields
>> >> tons of trash records at the beginning and the end of the dbf in the
>> >> browse window. this case almost always happens when any
>> >> crash of either the ups or the server occurs. what surprised us is
>> >> that
>> >> this EXTREMELY RARELY occured with our old version!
>> >> what is also funny is that in most cases, no data seem to have been
> lost
>> >> (except for the cases of partial record trashing),
>> >> only garbage gets appended to or inserted into the dbf from an unknown
>> >> source.
>> >>
>> >> We have reused 95% of the code in our old application and the business
>> >> logic is still the same. we do not use any buffering,
>> >> or transaction tracking. all updates to the dbf are directly written
>> >> followed by a flush command in the unload method of each
>> >> form - the same way as we used to do before. also, we use the same
>> >> data
>> >> session for all the application and all dbf files are
>> >> opened at the start of the application and are closed when the
>> >> application terminates.
>> >>
>> >> when you upgrade a development platform, you expect all the niceties
> and
>> >> advantages and reliability that comes with the term
>> >> UPGRADE. what you dont expect is going a couple of steps back with an
>> >> upgrade of at least 4 versions forward (fpw26 to vfp7),
>> >> and at least 2 upgrades forward for the os (win 98 se to winxp). but
> then
>> >> again, we might have made a mistake somewhere.
>> >>
>> >> i would appreciate any help or feedback regarding this issue and i
> thank
>> >> all those who reply to this post in advance for
>> >> their help and for sharing their experiences.
>> >>
>> >> regards
>> >>
>> >> anis
>> >>
>> >>
>> >
>> >
>>
>>
>


.

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