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3.2.2 Timers

A TDS client SHOULD implement the following three timers:

  • Connection Timer. Controls the maximum time spent during the establishment of a TDS connection. The default value SHOULD be 15 seconds. The implementation SHOULD allow the upper layer to specify a nondefault value, including an infinite value (for example, no timeout).

  • Client Request Timer. Controls the maximum time spent waiting for a query response from the server for a client request sent after the connection has been established. The default value is implementation-dependent. The implementation SHOULD allow the upper layer to specify a non-default value, including an infinite value (for example, no timeout).<21>

  • Cancel Timer. Controls the maximum time spent waiting for a query cancellation acknowledgement after an Attention request is sent to the server. The default value is implementation-dependent. The implementation SHOULD allow the upper layer to specify a nondefault value, including an infinite value (for example, no timeout).<22>

For all three timers, a client can implement a minimum timeout value that is as short as desired. If a TDS client implementation implements any of the timers, it MUST implement their behavior according to this specification.

A TDS client SHOULD request the transport to detect and indicate a broken connection if the transport provides such mechanism. If the transport used is TCP, it SHOULD use the TCP Keep-Alives [RFC1122] in order to detect a nonresponding server in case infinite connection timeout or infinite client request timeout is used. The default values of the TCP Keep-Alive values set by a TDS client are 30 seconds of no activity until the first keep-alive packet is sent and 1 second between when successive keep-alive packets are sent if no acknowledgement is received. The implementation SHOULD allow the upper layer to specify other TCP keep-alive values.

 
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