[Yazlist] Z39.50 operating situations

Marc Cromme marc at indexdata.dk
Thu Feb 14 12:06:08 CET 2008

Захаров Андрей wrote:
> hello, i am interesting in such questions:
> 1)As we know Z39.50 server can forward search requests to another Z39.50 
> servers)) and request path can be very long
>  Server1 -> Server2 -> Server3 -> ... ->ServerN
> Is their some kind of timeout or smth, or may be request depth can be 
> tuned up somehow?
> 2)and we can imagine situation that request path will be rounded
>  Server1 -> Server2 -> Server3 -> Server1
> Clarify this to me, please. how can we solve such kind of problem?
> 3) z39.50 server can make search in different places simultaneously
>                   / server1.db
> server1 -> |  server2
>                   \ server3

A Z39.50 server might implement it's search responses by asking one or 
multiple backend Z39.50 servers for the real data, but your client would 
not know.

You might want to look at one such product, Metaproxy, see the pages at

Especially these pages are interesting:

This might give you a better understanding of what's possible.

Your's Marc Cromme, Index Data

> imagine situation that first request is completed in 0.1 sec and 5 
> records found, second  2  sec and 20 records found, and third 20 sec 
> (for example) and 3000000 records found.
> 3.1) Does it mean, that request operation time equals 20 sec?
> 3.2) Can server1 return data partially, as its subrequests are complited? 
> 3.3) How does server1 make multiplexing for such great data volume, as 
> request result need to be sorted?
> 3.4) what if one of the referenced servers is down? how server1 can find 
> it out?
> Any useful help will be highly appreciated. Thanks
> Andrey
> PS sorry my english
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Marc Cromme
M.Sc and Ph.D in Mathematical Modeling and Computation
Senior Developer, Project Manager

Index Data Aps
Købmagergade 43, 2
1150 Copenhagen K.

tel: +45 3341 0100
fax: +45 3341 0101


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