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Q and A
Asked and Answered
Is there any reason to change the default memory optimization setting on Windows 2000
Datacenter Server from
Maximize data throughput for file sharing
to
Maximize data throughput for
network
operations
when you have already instructed DB2 to avoid file caching by setting the DB2
registry variable
DB2NTNOCACHE
to
ON
?
Chris Fierros responds:
Once the DB2 registry variable
DB2NTNOCACHE
is enabled and the instance has been restarted, the DB2
system controller process that manages the instance will avoid operating system file caching by
opening SMS and DMS file containers with a no-buffer file flag. Some of the other
utilities within
DB2, such as
LOAD
, will also attempt to avoid file caching.
The first reason to change the Windows 2000 Server optimization setting from
Maximize data
throughput for file sharing
to
Maximize data throughput for network operations
is to minimize the
operating system's use of memory for file caching. By doing so, you maximize DB2's working set
memory for buffer pools, sort heaps, and lock lists. Maximize data throughput for network operations
also
improves overall system performance by preventing the effects of double buffering.
The second reason is that if Windows 2000 Server's optimization setting is set to
Maximize data
throughput for file sharing
, processes outside the DB2 system controller process (and therefore not
governed by the
DB2NTNOCACHE
registry variable) can consume almost all remaining available memory
for file caching. This condition will almost always result in significant paging activity ý which,
of
course, is a bad thing. For example, a user exit process that copies archive log files or
database backup images wouldn't normally be aware of the
DB2NTNOCACHE
registry variable.
Finally, when the Windows 2000 Server optimization is changed to
Maximize data throughput for
network operations
, a larger portion of the operating system's non-paged fixed memory pool is
allocated for communication buffers, which — as the setting implies — maximizes throughput.
Return to
Scaling Up on Windows 2000 Datacenter Server
by Chris Fierros.
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