The following obtuse comment from another developer seems to confirm my
vague suspsicions but did not provide details, references, documentation or
work-around:
"New NVFS from garnet 5.4.9 can remove any resouce (locked or unlocked)
from closed unprotected database."
What this means: this sequence of code that was always broken now really
doesn't work:
DmOpenDatabase
DmGetResource
ptr = DmLockHandle
...
DmCloseDatabase
use ptr
You can only keep handles from databases as long as they are opened or
protected. This code would work if you added
DmOpenDatabase
DmProtectDatabase
DmGetResource
ptr = DmLockHandle
...
DmCloseDatabase
use ptr
This is because, starting with Palm OS 5.4.9, the NVFS implementation works
at the record level. The memory manager should keep a record active in the
DB cache if
1) it's locked, and
2) it belongs to a database that's open or protected
If you unlock a handle, the data can be purged, but it will be reloaded
from the file store if the handle is relocked. However, handles will be
invalidated when their associated DB is closed -- unless you protect the DB
first.
-- Ben Combee, Senior Software Engineer, Palm, Inc.
"Combee on Palm OS" weblog: http://palmos.combee.net/
Developer Forum Archives: http://news.palmos.com/read/all_forums/
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