Microsoft Exchange 2000 Operation Manual page 33

your server becomes low on kernel memory, your system becomes unresponsive. To regain
control of your server, you must restart it to free up the kernel memory.
Table 2.1 shows the registry parameters you might need to alter if you are to make perfor-
mance gains on servers with more than 1 GB RAM.
Table 2.1 Registry Parameters to Alter for Large Servers
Location Parameter
HKEY_LOCAL MsgHandle
_MACHINE\System Threshold
\CurrentControlSet (REG_DWORD)
\Services\SMTPSVC
\Queuing
HKEY_LOCAL MsgHandle
_MACHINE\System AsyncThreshold
\CurrentControlSet (REG_DWORD)
\Services\SMTPSVC
\Queuing
HKEY_LOCAL FileCache
_MACHINE\System MaxHandles
\CurrentControlSet (REG_DWORD)
\Services\Inetinfo
]Parameters
MaxMessageObjects is a registry parameter that correlates to the number of messages
that can be queued up at a given time by SMTP. Each e-mail message resident in the SMTP
queue uses at least 4 KB of memory; therefore, it is possible to run into a low memory
situation with a very large queue. Setting MaxMessageObjects lower reduces the maxi-
mum number of messages that can reside in the queue, thus decreasing the maximum
memory footprint for SMTP. After this limit is reached, each SMTP connection made to
the server will return with an out-of-memory error. For example, if MaxMessageObjects is
Chapter 2: Capacity and Availability Management
Default When to
Setting Change
Not present, To gain
but defaults additional
to 0x3e8 performance
when message
queues are
consistently
greater than
1,000
Not present, To gain
but defaults additional
to 0x3e8 performance
when message
queues are
consistently
greater than
1,000
Not present, If the
but defaults "MsgHandle
to 0x320 Threshold"
registry
parameter
value is
increased
from defaults
25
Recommended
Setting
Enough to
accomodate
the total
number of
messages in
the queues at
any one time.
You should not
raise the value
to greater than
15,000
decimal
Set to the
same
value as
"MsgHandle
Threshold"
0x258 (600)