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added additional doc on array size config

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Jeff Hill
2004-08-25 22:40:33 +00:00
parent 4e92e2f36c
commit 6f030c8030
1 changed files with 19 additions and 7 deletions
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src/ca/CAref.html
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@@ -676,13 +676,25 @@ placed in the variable EPICS_TS_MIN_WEST.</p>
<h3><a name="Configurin1">Configuring the Maximum Array Size</a></h3>
<p>The environment variable EPICS_CA_MAX_ARRAY_BYTES determines the size of
the largest array that may pass through CA. This parameter must be set
appropriately for both the CA client and the CA server. In EPICS R3.14 CA
maintains a free list of 16384 byte network buffers that are used for
ordinary communication. If EPICS_CA_MAX_ARRAY_BYTES&nbsp; is larger than
16384 then a second free list of larger data buffers is established when
clients request transportation of large arrays.</p>
<p>Starting with version R3.14 the environment variable
EPICS_CA_MAX_ARRAY_BYTES determines the size of the largest array that may
pass through CA. Prior to this version only arrays smaller than 16k bytes
could be transfered. The CA libraries maintains a free list of 16384 byte
network buffers that are used for ordinary communication. If
EPICS_CA_MAX_ARRAY_BYTES&nbsp; is larger than 16384 then a second free list
of larger data buffers is established and used only after a client send its
first large array request.</p>
<p>The CA client library uses EPICS_CA_MAX_ARRAY_BYTES to determines the
maximum array that it will send or receive. Likewise, the CA server uses
EPICS_CA_MAX_ARRAY_BYTES to determine the maximum array that it may send or
receive. The client does not influence the server's message size quotas and
visa versa. In fact the value of EPICS_CA_MAX_ARRAY_BYTES need not be the
same in the client and the server. If the server receives a request which is
too large to read or respond to in entirety then it sends an exception
message to the client. Likewise, if the CA client library receives a request
to send an array larger than EPICS_CA_MAX_ARRAY_BYTES it will return
ECA_TOLARGE.</p>
<h3><a name="Configurin2">Configuring a CA Server</a></h3>