The following equation shows the relationships between the units and factors involved: 100,000,000 bits 1 byte 5 seconds A simple way to determine the round trip time, is to use a command such as ping from one host to another and use the response times returned by ping.įor example, if a network has a bandwidth of 100 Mbps and a round trip time of 5ms, then the send and receive buffers should be at least (100*10^6) * (5/10^3) bits or approximately 62.5 Kilobytes. If sufficient memory is available, then using the maximum value for the SDU minimizes the number of system calls and overhead for Oracle Net Services.īandwidth-delay product is the product of network bandwidth and the round trip time of data going over the network. To change the default, change the DEFAULT_SDU_SIZE parameter in the sqlnet.ora file.įor example, if the majority of the messages sent and received by the application are smaller than 8KB, taking into account the 70 bytes for overhead, then setting the SDU to 8KB will likely produce good results.
BANDWIDTH DELAY PRODUCT PLUS
If the predominant message size plus 70 bytes exceeds the maximum SDU, then the SDU should be set such that the message size is divided into the smallest number of equal parts where each part is 70 bytes less than the SDU size. The SDU size should be 70 bytes larger than the predominant message size. You should consider changing the SDU size when the predominant message size is smaller or larger than 8192. For shared servers, only the client value must be changed because the shared server defaults to the maximum value. Configuring an SDU size different from the default requires configuring the SDU on both the client and server computers, unless you are using shared servers. The actual SDU size used is negotiated between the client and the server at connect time and is the smaller of the client and server values. The default SDU for a shared server is 65535 bytes. The default SDU for the client and a dedicated server is 8192 bytes. The SDU size can range from 512 bytes to 65535 bytes. If this assumption is true, then most of the time, the data is sent using one SDU buffer. Oracle Net assumes by default that the message size will normally vary between bytes, and infrequently, be larger than 8192 bytes. The amount of data provided to Oracle Net to send at any one time is referred to as the message size. When large amounts of data are being transmitted, increasing the SDU size can improve performance and network throughput. Adjusting the size of the SDU buffers relative to the amount of data provided to Oracle Net to send at any one time can improve performance, network utilization, and memory consumption. Oracle Net sends each buffer when it is filled, flushed, or when an application tries to read data.
Under typical database configuration, Oracle Net encapsulates data into buffers the size of the session data unit (SDU) before sending the data across the network.
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