Re: USE DATABASE from 4D client

[Alan Chan via 4D_Tech]

I might be missing something obvious. Why not simply using SQL login to access 
external database and the data could be accessed by multiple 4D clients.

SQL LOGIN($externaAddress;$user;$pswd;*)
If (OK=1)
Begin SQL
//do whatever SQL query
End SQL
SQL LOGOUT
End if 

Alan Chan

4D iNug Technical <4d_tech@lists.4d.com> writes:
>If I have an external datafile held on the server how do I access it
>(purely for lookup) from a 4D client?

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Re: USE DATABASE from 4D client

[David Samson via 4D_Tech]

Keisuke Miyako wrote:

>rather activating the "execute on server" method property,
>I would recommend using the REMOTE keyword:

Does that allow multiple users to access it simultanously?

Thanks for the reply,
David
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Re: USE DATABASE from 4D client

[David Samson via 4D_Tech]

David Adams wrote:

>On another note, is there some reason that you can't or don't want to
>download the file to the clients?

It is a 28 million record postal address file so segmenting won't work. I
have thought of copying it over to the clients but then the issue of
keeping it updated raises its head.

I would much prefer one central database. At present it is in the main 4D
datafile but bloats it somewhat.

Thank you David,
David
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Re: USE DATABASE from 4D client

[bob.miller--- via 4D_Tech]

RE> rather activating the "execute on server" method property,
I would recommend using the REMOTE keyword:

http://doc.4d.com/4Dv15/4D/15/USE-DATABASE.300-2288124.en.html



I don't understand how this would make any difference; the REMOTE database 
would still be held open until AUTO_CLOSE was called, or the calling 
process ended - so the database would remain locked to other users.

How does REMOTE allow the database to remain open (so there is minimal 
overhead to call USE DATABASE) to other users?


Bob Miller
Chomerics, a division of Parker Hannifin Corporation


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Re: USE DATABASE from 4D client

[Keisuke Miyako via 4D_Tech]

rather activating the "execute on server" method property,
I would recommend using the REMOTE keyword:

http://doc.4d.com/4Dv15/4D/15/USE-DATABASE.300-2288124.en.html

2017/05/30 23:25、David Samson via 4D_Tech 
<4d_tech@lists.4d.com> のメール：

One suggestion I saw on the NUG was to access it from the server using the
"Execute on Server" property on a method and then apparently the locking is
taken care of by the 4D server.



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Re: USE DATABASE from 4D client

[David Adams via 4D_Tech]

David,

Interesting question about Execute on server, I hope we get a good answer.
I suspect that you might be right. If everything is going through Execute
on server, it's all running on one machine. At that point, I guess you
would not use AUTO_CLOSE and would allow 4D to manage the access. Hmm. I'm
curious to hear more about this.

On another note, is there some reason that you can't or don't want to
download the file to the clients? There probably is (it's not hard to
imagine various good reasons.) If so, is there a way that you can segment
the data and download some of it to the clients? Sometimes a data set has
values that can be shared/duplicated, etc. mixed in with some that can't.
If you've got a situation like that, you could at least pull out the
okay-to-download data into one file for copying to the clients. That might
beat the network traffic and bottleneck of a single shared file on the
server machine.
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USE DATABASE from 4D client

[David Samson via 4D_Tech]

I asked this question some time ago but with the current flurry of interest
in external databases I will have another go. NB no components involved
here.

If I have an external datafile held on the server how do I access it
(purely for lookup) from a 4D client?

What I tried was to use SQL as follows:

Begin SQL
USE DATABASE DATAFILE 'F:\AuthCodeEXT.4DD';
select LocAuthCode_LOOKUP.OSLAUA

from LocAuthCode_LOOKUP
where PCD2 = :cPC_Search
into :acLocAuthCodes;

USE DATABASE SQL_INTERNAL;
End SQL

 and then to release the datafile with AUTO_CLOSE.

This works fine in a very low usage context.

I would like to use it in a busier scenario but am concerned that the
datafile would often be locked.

One suggestion I saw on the NUG was to access it from the server using the
"Execute on Server" property on a method and then apparently the locking is
taken care of by the 4D server.

Has anybody tried this arrangement in a busy database (40-50 users and
additional web cleints)?

David Samson
Manchester
UK
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