rpc_set_async_ack.3ncs

<B>Digital的Unix操作系统VAX 4.2源码</B>

.TH rpc_set_async_ack 3ncs
.SH Name
rpc_set_async_ack \- set or clear asynchronous-acknowledgement mode (client only)
.SH Syntax
.nf
#include <idl/c/rpc.h>

void rpc_$set_async_ack (\fIstate\fP)
unsigned long \fIstate\fP;
.fi
.\".SH SYNOPSIS (PASCAL)
.\".DS
.\"\fB%include '/usr/include/idl/pas/rpc.ins.pas'\fR
.\"
.\"\fBprocedure rpc_$set_async_ack(\fR
.\"\fBin \fIon\fB: unsigned32);\fR
.\".DE
.SH Arguments
.TP 20
.I state
If "true" (nonzero), asynchronous-acknowledgement mode is set.
If "false" (zero), synchronous-acknowledgement mode is set.
.SH Description
The 
.PN rpc_$set_async_ack
.NXR "Interface to the Remote Procedure Call" "rpc_set_async_ack"
call sets or clears
asynchronous-acknowledgement mode in a client.
.PP
.\".SS MS-DOS Systems and Systems with CPS
.\"On MS-DOS systems and on systems that have Concurrent Programming Support,
.\"\fBrpc_$set_async_ack\fR has no effect.
.\"These systems always use asynchronous-acknowledgement mode.
.\".SS Other Systems
Synchronous-acknowledgement mode is the default.
Calling
.PN rpc_$set_async_ack
with a nonzero value for 
.I state
sets asynchronous-acknowledgement mode.
Calling it with a zero value for 
.I state
sets synchronous-acknowledgement mode.
.PP
After a client makes a remote procedure call and receives a reply from a server,
the RPC runtime library at the client acknowledges its receipt of the reply.
This
"reply acknowledgement"
can occur
either synchronously (before the runtime library returns to the caller)
or asynchronously (after the runtime library returns to the caller).
.PP
It is generally good to allow asynchronous reply acknowledgements.
Asynchronous-acknowledgement mode can save
the client runtime library from making explicit reply acknowledgements,
because after a client receives a reply,
it may shortly issue another call that can act as an implicit acknowledgement.
.PP
Asynchronous-acknowledgement mode requires that an
"alarm"
be set to go off sometime after the remote procedure call returns.
Unfortunately, setting the alarm can cause two problems:
.RS
.IP 1  
There may be only one alarm that can be set, and the application
itself may be trying to use it.
.IP 2  
If, at the time the alarm goes off, the application is blocked
in a system call that is doing I/O to a
"slow device" (such as a terminal),
the system call will return an error (with the EINTR errno);
the application may not be coded to expect this error.
If neither of these problems exists,
the application should set asynchronous-acknowledgement mode to get
greater efficiency.
.RE
.SH Files
.PN /usr/include/idl/c/rpc.h
.br
.PN /usr/include/idl/rpc.idl
.SH See Also
intro(3ncs)