Chapter 2: Capacity and Availability Management
25
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
Default
When to
Recommended
Setting
Change
Setting
HKEY_LOCAL
MsgHandle
Not present,
To gain
Enough to
_MACHINE\System
Threshold
but defaults
additional
accomodate
\CurrentControlSet
(REG_DWORD)
to 0x3e8
performance
the total
\Services\SMTPSVC
when message
number of
\Queuing
queues are
messages in
consistently
the queues at
greater than
any one time.
1,000
You should not
raise the value
to greater than
15,000
decimal
HKEY_LOCAL
MsgHandle
Not present,
To gain
Set to the
_MACHINE\System
AsyncThreshold
but defaults
additional
same
\CurrentControlSet
(REG_DWORD)
to 0x3e8
performance
value as
\Services\SMTPSVC
when message
“MsgHandle
\Queuing
queues are
Threshold”
consistently
greater than
1,000
HKEY_LOCAL
FileCache
Not present,
If the
0x258 (600)
_MACHINE\System
MaxHandles
but defaults
“MsgHandle
\CurrentControlSet
(REG_DWORD)
to 0x320
Threshold”
\Services\Inetinfo
registry
]Parameters
parameter
value is
increased
from defaults
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
