additional network memory

additional network memory sets the maximum size of additional memory that can be used for network packets that are larger than the default packet size. Adaptive Server rounds down the value you enter to the nearest 2K value. The default value indicates that no extra space is allocated for large packets.

When a login requests a large packet size, Adaptive Server verifies it has sufficient memory available to satisfy the request. If it does, the login continues. If it does not, Adaptive Server finds the largest available block of memory and tries the appropriate size (which is a multiple of default network packet size) less than the largest memory block. If that fails, Adaptive Server decreases the value of the request by the numbe of bytes equal to default network packet size, if this is available. Adaptive Server continues for 10 iterations or until the size equals the value of default network packet size, whichever comes first. On the tenth iteration, Adaptive Server uses the value of the default network packet size for the packet size.

If you increase max network packet size but do not increase additional network memory, clients cannot use packet sizes that are larger than the default size, because all allocated network memory is reserved for users at the default size. Adaptive Server guarantees that every user connection can log in at the default packet size. In this situation, users who request a large packet size when they log in receive a warning message telling them that their application will use the default size.

If you request a large packet size, Adaptive Server checks if the memory is available to satisfy the request.

• If the memory is available, the login continues

• If the memory is not available, Adaptive Server finds the largest available block of memory and tries again with a packet size equal to the largest block less the default network packet size. If that fails, Adaptive Server retries, but reduces the size of the request by the value of default network packet size. It repeats this process for 10 attempts until the packet size is equal to the configured default network packet size. At the tenth attempt, Adaptive Server drops the packet size to the configured default network packet size, since this size is always available. The "additional network memory" parameter is used to guarantee memory is available for these larger packet size allocations

Increasing additional network memory may improve performance for applications that transfer large amounts of data. To determine the value for additional network memory when your applications use larger packet sizes:

• Estimate the number of simultaneous users who will request the large packet sizes, and the sizes their applications will request,

• Multiply this sum by three, since each connection needs three buffers,

• Add two percent for overhead for 32-bit servers or four percent for 64-bit servers, and

• Round the value to the next highest multiple of 2048.

For example, if you estimate these simultaneous needs for larger packet sizes:

You should set additional network memory to 75,776 bytes.

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