on 1/31/04 7:39 PM, Robert Brenstein at rjb /at/ rz DO.T uni-potsdam.de wrote:
>>> -- option to open databases in read-only mode (as parameter to open
>>> or separate call) regardless whether it is on read-only or read-write
>>> medium
>>
>> Aha, as flag on open....
>> I afraid not works.
>>
>> Assume files are not marked.
>> One app open as read only. Ok.
>> But other open as read/write => BIG PROBLEMS.
>
> I am not sure problems are so big (at least in my ignorance :)
>
> So what if the other app modifies a content of the field. The first
> app will get the new content (ya, live cursor modifiable by others).
> That is often desirable. If the 2nd app deletes a record, first
> should get an error "recordDeleted". If 2nd app makes any structure
> changes, 1st app returns "cursorNoLongerValid" error. Do I miss
> anything?
Yes,
Now assume that SECOND app also do OPEN in READ/WRITE mode.
Ho I can prevent this?
This is why flag on file protect.
Of course, it is possible to start again speak:
WRITE apps, must set some LOCKS on files...
But this is again return to SHARED ACCESS to files.
> But, you can (at least initially) restrict that if a db is open for
> read, other apps can open it also for read only. A lock file could be
> used if there is no better way. (A change file could be used to pass
> level of changes from the read/write up.)
Use of lock file, means adding into kernel not needed overhead.
Valentina server is an answer for such tasks.
--
Best regards,
Ruslan Zasukhin [ I feel the need...the need for speed ]
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