Hi Dave,
congratulations - a very convincing example.
> Try no. 1: on the first pass, it got to record 1718, then gave me a Fatal
> Alert: "Preferences.c, Line: 264, Pref DB Open Error"
Hard to believe. This normally signifies another Palm OS bug in the prefs
handling. (They forget to close the database.) But how could this problem
propagate to DmQueryRecord()?
Did you try using DmGetRecord? I think we'll try to make similar tests...
Best regards,
Jan Slodicka
----- Original Message -----
From: "Dave Carrigan" <[EMAIL PROTECTED]>
To: "Palm Developer Forum" <[email protected]>
Sent: Thursday, March 10, 2005 11:54 PM
Subject: Newer and greater NVFS woes
> I think I have found another bug with the NVFS implementation on the
> T5. It appears that if you routinely read large amounts of data from a
> database, you will end up corrupting the NVFS cache, which causes memory
> errors when you try to query a record, and eventually crashes the
> device.
>
> In my tests, I first created a large database -- 2500 records ranging from
> 10-20k in size, for a total of around 35MB. I then went in a loop doing:
>
> for (;;)
> for (UInt16 i = 0; i < DmNumRecords(db); ++i) {
> MemHandle rec(DmQueryRecord(db, i));
> while (rec == NULL) {
> // Display result of DmGetLastErr()
> rec = DmQueryRecord(db, i);
> }
>
> UInt8* buf(new UInt8[MemHandleSize(rec)]);
> MemMove(buf, MemHandleLock(rec), MemHandleSize(rec));
> delete[] buf;
> MemHandleUnlock(rec);
> }
> }
>
> Here are my results:
>
> Try no. 1: on the first pass, it got to record 1718, then gave me a Fatal
> Alert: "Preferences.c, Line: 264, Pref DB Open Error" and I had to reset
> the device with a paper clip.
>
> Try no. 2: on the first pass, it got to record 1614, then DmQueryRecord
> returned error 513 (dmErrMemError) when it tried to read the next
> record, then it gave me a Fatal Exception with no text, and I had to
> reset the device with a paper clip.
>
> Try no. 3: on the first pass, DmQueryRecord returned error 513
> (dmErrMemError) on record 1890 four times, then was actually able to
> read the record. It continued to record 1967, where I got another error
> 513 (twice), then again on record 2198, where I got another error 513
> (five times) and finally it finished. On the second pass, DmQueryRecord
> returned error 513 on records 129 (x2), 992 (x1), 1079 (x1), 1110 (x1),
> 1238 (x1), 1478 (x1), 2428 (x2). On the third pass, DmQueryRecord
> returned error 513 on record 9. I tapped the house to exit the
> application and got a Fatal Alert: "VFSDBCache.c, Line: 6731,
> CloseRecord() had problems reloading a record.", and I had to reset the
> device with a paper clip.
>
> On try no. 4 and 5, I got error 513 on records 1842 and 2436,
respectively,
> then got a Fatal Exception with no text and had to reset the device.
>
> If you would like to see my test program and try to duplicate my results,
> send me private email.
>
> --
> Dave Carrigan
> Seattle, WA, USA
> [EMAIL PROTECTED] | http://www.rudedog.org/ | ICQ:161669680
> UNIX-Apache-Perl-Linux-Firewalls-LDAP-C-C++-DNS-PalmOS-PostgreSQL-MySQL
>
> --
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