Controls the size of the duplicate request cache that detects RPC level retransmissions on connection oriented transports. This cache is indexed by the client network address and the RPC procedure number, program number, version number, and the transaction ID. This cache avoids processing of retransmitted requests that might be non-idempotent.
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The cache is dynamically sized, but the hash queues that provide fast access to the cache are statically sized. Making the cache very large might result in long search times to find entries in the cache.
Do not set the value of this parameter to 0. It prevents the NFS server from handling non-idempotent requests.
Examine the value of this parameter if false failures are being seen by NFS clients. For example, if an attempt to create a directory fails, but the directory is actually created, it is possible that a retransmitted MKDIR request was not detected by the server.
The size of the cache should match the load on the server. The cache records non-idempotent requests and so only needs to track a portion of the total requests. It does need to hold the information long enough to be able to detect a retransmission on the part of the client. Typically, the client timeout for connection oriented transports is very long, about 1 minute. Thus, entries need to stay in the cache for fairly long times.