Configuring core group socket buffers

Most operating systems provide program interfaces for performing operations involving the sending and receiving of data over sockets. Most operating systems also provide administrative capabilities to control the amount of memory allocated per socket that is used as data buffers.

Before you begin

• Check your operating system settings that are relevant to TCP sockets. For example, if you are using an AIX® operating system, check the values that are specified for the tcp_sendspace, tcp_recvspace, and sb_max settings. Similarly on a Linux® operating system, check the values that are specified for the tcp_rmem, and tcp_wmem settings.
• Use the performance monitoring infrastructure for the product to determine the average message size that the core group transport handles. If your operating system setting for the default buffer size is smaller than the average message size, make one of the following changes:
  • Change the default buffer size setting for your operating system. However, this action might be inappropriate because it might affect the operation of other applications running on this operating system.
  • Change the size of the socket buffer that the core group transport obtains. The value that is specified for the IBM_CS_SOCKET_BUFFER_SIZE core group custom property determines the size of the socket buffer that the core group transport obtains.

  Table 1. Socket Buffer type, values for the property, and memory allocation . The following table shows the relationship between the values that can be specified for this property and the underlying memory allocation size per socket buffer type:

  Socket Buffer Type	Property set to 0	Property set to 1	Property set to 2	Property set to 3
  Unicast receive	Operating system default buffer size is used.	Buffer size is 64 kilobytes	Buffer size is 256 kilobytes	Buffer size is 1 megabyte
  Unicast send	Operating system default buffer size is used.	Operating system default buffer size is used.	Buffer size is 64 kilobytes	Buffer size is 128 kilobytes
  Multicast receive	Operating system default buffer size is used.	Buffer size is 512 kilobytes	Buffer size is 1 megabyte	Buffer size is 3 megabytes

About this task

You might want to change the size of your core group buffers in the following circumstances:

• You are directed to do so by IBM® Support
• You are directed to do so during the course of installing another WebSphere® product.
• You want to change the behavior of the core group transport without affecting the behavior of other sockets.
• You are trying to tune the network communication path of your system to your application.

To change the socket buffer space that the core group transport allocates:

1. In the administrative console, click Servers > Core Groups > Core group settings core_group_name.
2. Under Additional Properties, click Custom properties.
3. Change the value that is specified for the IBM_CS_SOCKET_BUFFER_SIZE custom property.

   If the IBM_CS_SOCKET_BUFFER_SIZE property already exists, click the property name and specify either 0, 1, 2, or 3.

   If this property does not already exist, click New and create it:

   1. In the Name field, specify IBM_CS_SOCKET_BUFFER_SIZE.
   2. In the Value field specify one of the following strings:
      • 0
      • 1
      • 2
      • 3
4. Click OK and then click Review.
5. Select Synchronize changes with nodes, and then click Save.
6. Restart all members of the core group.

Results

After the servers restart, the core group members all run with the new socket buffer size settings.