When requesting a file on the network, the request is handled by the MUP, and depending on configuration, then the request is passed to the Microsoft Network SMB Redirector (MrxSmb).
The SMB Redirector keeps a cache of recent accessed files, but by default it only caches short-filenames. If frequently accessing the same network files (Like ex. a database), then performance can be improved by using 8.3 short-filenames. Another solution is to configure the SMB redirector to cache long-filenames.

[HKEY_LOCAL_MACHINE \SYSTEM \CurrentControlSet \Services \MRxSmb \Parameters]
InfoCacheLevel = 16 (Default = 1, Disabled = 0, Both Long & Short = 16)

Note WinXP requires SP2 to recognize this registry-key. More Info MS KB834350

Note Win2k requires a post SP4 hotfix (Included in the Update Rollup) from Microsoft to recognize this registry-key. More Info MS KB843418

Note there is a limit for how many file handles the client redirector will keep it in its cache:

[HKEY_LOCAL_MACHINE \SYSTEM \CurrentControlSet \Services \LanmanWorkstation \Parameters]
DormantFileLimit = 45 (Default = 45)

More Info MS KB890584

Note the client redirector has a scavenger thread, which cleans old file handles from its cache. One can configure how often it should look for old handles to remove (WinXP/Win2k3):

[HKEY_LOCAL_MACHINE \SYSTEM \CurrentControlSet \Services \LanmanWorkstation \Parameters]
ScavengerTimeLimit = 30 (Default = Every 10 secs, Min = 10 secs, Max = 120 secs)

More Info MS KB816073
More Info MS KB890553

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