Re: asyn IMAX data transfer exceeding EPICS_CA_MAX_ARRAY_BYTES

["Siddons, David via Tech-talk" <tech-talk at aps.anl.gov>]

Hi Marco,

   Is EPICS_CA_MAX_ARRAY_BYTES set on both ends of the link?

Pete.

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From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Marco A. Barra Montevechi Filho via Tech-talk <tech-talk at aps.anl.gov>
Sent: Tuesday, March 15, 2022 3:39 PM
To: tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: asyn IMAX data transfer exceeding EPICS_CA_MAX_ARRAY_BYTES

 

Hello all

Im debugging an EPICS asyn IOC which was working fine until now. The st.cmd of the IOC has a line which loaded asynRecord.db:

dbLoadRecords("$(ASYN)/db/asynRecord.db","P=$(DEV),R=asynEth,PORT=E873_ETH,ADDR=0,OMAX=256,IMAX=256")

and caput caget BL:H:EQ:asynEth.IFMT 1 (Hybrid)

caget BL:H:EQ:asynEth.BINP

in the IOC machine returned an array of numbers without any problem. However, it is recovering an array from a file much alrger than 256, so i suppose it just threw parts of the file away.
We wanted to get more of the file, so we raised IMAX to 350000 and defined the env variable EPICS_CA_MAX_ARRAY_BYTES=15728645. SO we got the error

caget MGN:A:E873:DIAG:A:asynEth.BINP

CA.Client.Exception...............................................

    Warning: "The requested data transfer is greater than available memory or EPICS_CA_MAX_ARRAY_BYTES"

    Context: "op=0, channel=MGN:A:E873:DIAG:A:asynEth.BINP, type=DBR_TIME_CHAR, count=16406, ctx="server unable to load read (or subscription update) response into protocol buffer PV="MGN:A:E873:DIAG:A:asynEth" max bytes=16408""

    Source File: ../getCopy.cpp line 92

    Current Time: Tue Mar 15 2022 16:32:11.936961493

..................................................................

Read operation timed out: some PV data was not read.

MGN:A:E873:DIAG:A:asynEth.BINP 350000 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0  (the zeroes continue)

So we tried lowering IMAX to 16406 but still the error persisted:

CA.Client.Exception...............................................

    Warning: "The requested data transfer is greater than available memory or EPICS_CA_MAX_ARRAY_BYTES"

    Context: "op=0, channel=MGN:A:E873:DIAG:A:asynEth.BINP, type=DBR_TIME_CHAR, count=16406, ctx="server unable to load read (or subscription update) response into protocol buffer PV="MGN:A:E873:DIAG:A:asynEth" max bytes=16408""

    Source File: ../getCopy.cpp line 92

    Current Time: Tue Mar 15 2022 16:32:11.936961493

..................................................................

Read operation timed out: some PV data was not read.

MGN:A:E873:DIAG:A:asynEth.BINP 16406 0 0 0 0 0 0

does anyone know if we are doing something wrong or forgetting something? I dont think memory should be the problem here... Where do these "max bytes=16408" come from?

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