BUG: Slow TCP/IP Connection to SQL Server from NT & DOS Client (128617)
The information in this article applies to:
- Microsoft SQL Server 4.2x
This article was previously published under Q128617
BUG# NT: 8507 (4.21a)
SYMPTOMS
The initial TCP/IP sockets connection to SQL Server from Microsoft Windows
NT and MS-DOS clients using DBMSSOCN.DLL and DBMSSOC.EXE, respectively, can
be very slow due to the abnormal IP address resolution behavior in these
client-side Network Libraries (Net-Library).
The TCP/IP client-side sockets Net-Libraries for Windows NT and MS-DOS
(DBMSSOCN.DLL and DBMSSOC.EXE) try to resolve host address even if the SQL
Server's IP address is already hardcoded in the connection string.
This unnecessary attempt to resolve IP address can cause substantial delay
in the initial connection. This is because the Net-Library tries to use the
IP address as the host name to resolve the host address, which will
eventually fail as expected. However, the failed attempts can cause
substantial delay as the client has to wait for either the broadcast or
point-to-point connection timeouts, depending on how the client is
configured for IP host resolution.
CAUSE
The Net-Library calls GetHostByName() to resolve IP address whether a host
name is used or not. Therefore, if an IP address is used instead of a host
name, this call will cause the workstation to broadcast unnecessarily if b-
node is used, which in turn causes the connection delay.
WORKAROUND
You can workaround this problem by using a host name rather than the
IP address in the connection string. When you use the host name, the
client will try to resolve its address using the appropriate host
address resolution mechanism configured on the client. Because the host
name should be resolved successfully, the time it takes is much
shorter than the failed address resolution attempts if you hardcode
the IP address. Based on this, there are two workarounds:
- Configure the client to use WINS: If WINS server is available on
your network, it is recommended that WINS is used for IP address
resolution due to its efficiency as a point-to-point node (p-node).
-or-
- If WINS is not used on the client, typically the client is
defaulted to Microsoft Modified b-node, which means the client will
check the LMHOSTS cache first, and then broadcast, and finally look
it up in LMHOSTS. If broadcast can not resolve the address (because
the server is on the other side of a router, for example), you can
add the host name and address in the LMHOSTS file for lookup. Using
this method, the first connection will still be a little slow due to
the failed broadcast, but any subsequent connection attempts should
be fast because the address is available in cache.
STATUS
Microsoft has confirmed this to be a problem in Microsoft SQL Server
version 4.21a. We are researching this problem and will post new
information here in the Microsoft Knowledge Base as it becomes available.
| Modification Type: | Major | Last Reviewed: | 4/18/1999 |
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| Keywords: | kbenv kbusage KB128617 |
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