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INF: Number of Connections for SQL Server 6.5 Win16 Clients

This article was previously published under Q150909
This article has been archived. It is offered "as is" and will no longer be updated.
When you use 16-bit Windows client tools, such as ISQL/W, with the DB-Library from SQL Server version 6.5 to connect to SQL Server 6.0 or SQLServer 6.5, you might not be able to make as many simultaneous connectionsto SQL Server as you would have if you used the the SQL Server version 6.0version of the DB-Library. The DB-Library involved is either W3DBLIB.DLL orMSDBLIB3.DLL.

The network library used is irrelevant.

The number of connections is affected by the Network Packet Sizeconfiguration value of SQL Server. The smaller the Network Packet Size(minimum 512 bytes), the more simultaneous connections you can make fromthe same DB-Library client, because the larger the network packet size, themore system resources are used on the Windows 3.x client.

When the Windows 3.1x client runs out of system resources, you will get thefollowing message:
Msg. No.: 10000 Severity: 8 State: 0
Error: Unable to allocate sufficient memory
OS Error: 12 Unable to allocate sufficient memory
Starting with version 6.5, the 16-bit Windows DB-Library will use thenetwork packet size configuration specified on the server side under thefollowing conditions:
  1. The client application using the DB-Library function DBSETLVERSION andspecified DBVER60 to take advantage of functionality of SQL Server version6.0 or 6.5.
  2. The client application did not specify the packet size using the
DBSETLPACKET DB-Library function.

The ISQL/W client tool, starting from version 6.0, used dbsetlversion toset the DB-Library client behavior to version 6.0. However, it does notspecify the network packet size to be used on the client. When the tool isused with 16-bit DB-Library from SQL Server 6.0, the network packet size isdefaulted to 512 bytes, which allows you to make a fair number ofsimultaneous connections from the same client. Depending on the particularconfiguration of your particular computer, different number of connectionscan be made. However, it is not uncommon to make 15 named pipe connectionsfrom the same client.

Using the ISQL/W and the 16-bit DB-Library from version 6.5, if the NetworkPacket Size on the server side is configured to be 512, you should be ableto make the same number of connections from the same client. However, ifthe Network Packet Size is set to 4096 bytes (which is the defaultconfiguration value) on the server side, if you were able to make 15 namedpipes connections before when the packet size was 512, you can probablyexpect to make only 5 simultaneous named pipe connections with the packetsize set to 4096.
limitation TDS

Article ID: 150909 - Last Review: 09/30/2013 22:10:05 - Revision: 3.0

Microsoft SQL Server 6.0 Standard Edition, Microsoft SQL Server 6.5 Standard Edition

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