INF: Number of Connections for SQL Server 6.5 Win16 Clients (150909)

SUMMARY

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 SQL Server 6.5, you might not be able to make as many simultaneous connections to SQL Server as you would have if you used the the SQL Server version 6.0 version of the DB-Library. The DB-Library involved is either W3DBLIB.DLL or MSDBLIB3.DLL.

The network library used is irrelevant.

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

When the Windows 3.1x client runs out of system resources, you will get the following message:

Msg. No.: 10000 Severity: 8 State: 0
Error: Unable to allocate sufficient memory
OS Error: 12 Unable to allocate sufficient memory

MORE INFORMATION

Starting with version 6.5, the 16-bit Windows DB-Library will use the network packet size configuration specified on the server side under the following conditions:

The client application using the DB-Library function DBSETLVERSION and specified DBVER60 to take advantage of functionality of SQL Server version 6.0 or 6.5.
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 to set the DB-Library client behavior to version 6.0. However, it does not specify the network packet size to be used on the client. When the tool is used with 16-bit DB-Library from SQL Server 6.0, the network packet size is defaulted to 512 bytes, which allows you to make a fair number of simultaneous connections from the same client. Depending on the particular configuration of your particular computer, different number of connections can be made. However, it is not uncommon to make 15 named pipe connections from the same client.

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