Distributed Programming Queries

Hey,
My group at uni is currently trying to make a program that runs via a multi-threaded client/server, however its not going too well.
It needs to authorize the users as they log on and store their details, as well as having a chat lobby and running a game (storing its highscores etc).
anyone got any advice? got any example code? ;-)
currently we are looking at putting the server and the chat lobby together, while making the client and game do the rest of the work (the game is going to be P2P)
i have included the spec for the project as a guide to the kind of help we need:
- Authorize and Register (if not alredy authorized)
- Store current information on clients (name, IP etc)
- provide a method of transferring player details between server/client
- Store scores from game on server (i.e. high score table)
- connection stats (i.e. no of connections, player stats (i.e. wins/losses/games played))
- the client needs to mirror these actions as well as allow the play between two other players
we hope this helps in choosing the advice to give and we thank you in advance for everyones help.

What you need to do is this - Learn the Java language
Your question does not merit an actual answer. Most people are seeking answers to technical questions, or planning help.
You need nither of these.
You are set right now. You know what you want to do, and what needs to be done. That's the hardest part of programming.
I would say that you should buy some books on Java for your development team, learn them, and then hire a Java consultant to come in and be the "technical director" for your project.

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Sabine,
Do you want to make changes to you application only on a development machine then update production?
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Hi,
In a distributed cache scheme ( in multiple servers/jvm).
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Hi,
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Hi,
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Hi all,
I would like to perform a sql query between two database servers (Oracle).
For example :
select server1.employees.id, server1.employees.name, server2.accounts.balance, server2.accounts.employeeId where server1.employees.id = server2.accounts.employeeId;
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CREATE DATABASE LINK linkname CONNECT TO user IDENTIFIED BY pass USING sqlnet_alias;
select * from tab1, tab2@linkname where ...
Steve

Need some clarification in the following programs

Hi ABAPers
I am learning ABAP programming. I am having some doubts in some programs which are there in the book TEACH YOURSELF ABAP/4 in 21 Days.
I hope you will clear all my doubts
1)     when I execute this program it is giving me error message and I am unable to resolve the error in it.
I dont remember the error message but it is something related to data conversion.
Listing 9.5 Variables Filled with Characters Other than Blanks or Zeros Using the WITH Addition of the CLEAR Statement
1 report ztx0905.
2 tables ztxlfa1.
3 data: f1(2) type c value 'AB',
4       f2(2) type c,
5       f3    type i value 12345,
6       begin of s1,
7           f1(3) type c value 'XYZ',
8           f2    type i value 123456,
9           end of s1.
10 write: / 'f1=''' no-gap, f1 no-gap, '''',
11        / 'f2=''' no-gap, f2 no-gap, '''',
12        / 'f3=''' no-gap, f3 no-gap, '''',
13        / 's1-f1=''' no-gap, s1-f1 no-gap, '''',
14        / 's1-f2=''' no-gap, s1-f2 no-gap, '''',
15        / 'ztxlfa1-lifnr=''' no-gap, ztxlfa1-lifnr no-gap, '''',
16        / 'ztxlfa1-land1=''' no-gap, ztxlfa1-land1 no-gap, '''',
17        /.
18 clear: f1 with 'X',
19        f2 with f1,
20        f3 with 3,
21        s1 with 'X',
22        ztxlfa1 with 0.
23 write: / 'f1=''' no-gap, f1 no-gap, '''',
24        / 'f2=''' no-gap, f2 no-gap, '''',
25        / 'f3=''' no-gap, f3 no-gap, '''',
26        / 's1-f1=''' no-gap, s1-f1 no-gap, '''',
27        / 's1-f2=''' no-gap, s1-f2 no-gap, '''',
28        / 'ztxlfa1-lifnr=''' no-gap, ztxlfa1-lifnr no-gap, '''',
29        / 'ztxlfa1-land1=''' no-gap, ztxlfa1-land1 no-gap, ''''.
according the book the output should be
The code in Listing 9.5 produces this output:
f1='AB'
f2=' '
f3='    12,345 '
s1-f1='XYZ'
s1-f2='   123,456 '
ztxlfa1-lifnr='          '
ztxlfa1-land1='   '
f1='XX'
f2='XX'
f3='50,529,027 '
s1-f1='XXX'
s1-f2='1482184792 '
ztxlfa1-lifnr='##########'
ztxlfa1-land1='###'
can you please explain me this program.
2)     This program is giving me the following error message at line 7.
ALPHA AND IT-F1 ARE TYPE- INCOMPATIBLE.
The program is as follows.
Listing 12.9 Deleting Rows from an Internal Table Can also be Done Using the delete Statement
1 report ztx1209.
2 data: begin of it occurs 12,
3            f1,
4            end of it,
5            alpha(12) value 'ABCDEFGHIJKL'.
6
7 do 12 times varying it-f1 from alpha0 next alpha1.
8      append it.
9      enddo.
10
11 loop at it.
12     write: / sy-tabix, it-f1.
13     endloop.
14
15 delete it index 5.
16 skip.
17 loop at it.
18     write: / sy-tabix, it-f1.
19     endloop.
20
21 delete it from 6 to 8.
22 skip.
23 loop at it.
24     write: / sy-tabix, it-f1.
25     endloop.
26
27 delete it where f1 between 'B' and 'D'.
28 skip.
29 loop at it.
30     write: / sy-tabix, it-f1.
31     endloop.
32
33 loop at it where f1 between 'E' and 'J'.
34     delete it.
35     endloop.
36
37 skip.
38 loop at it.
39     write: / sy-tabix, it-f1.
40     endloop.
41
42 read table it with key f1 = 'K' binary search.
43 write: /, / 'sy-subrc=', sy-subrc, 'sy-tabix=', sy-tabix, / ''.
44 if sy-subrc = 0.
45     delete it index sy-tabix.
46     endif.
47
48 skip.
49 loop at it.
50     write: / sy-tabix, it-f1.
51     endloop.
52
53 free it.
And the out put according to the book is as follows
The code in Listing 12.9 produces this output:
         1 A
         2 B
         3 C
         4 D
         5 E
         6 F
         7 G
         8 H
         9 I
        10 J
        11 K
        12 L
         1 A
         2 B
         3 C
         4 D
         5 F
         6 G
         7 H
         8 I
         9 J
        10 K
        11 L
         1 A
         2 B
         3 C
         4 D
         5 F
         6 J
         7 K
         8 L
         1 A
         2 F
         3 J
         4 K
         5 L
         1 A
         2 K
         3 L
sy-subrc=     0 sy-tabix=          2
         1 A
         2 L
How to rectify the error in this program.
3)     In this program I want to ask is there any way that I can be able to see the write statement output which is there in the initialization event block. If yes then how .
(Note I dont want to remove the paramter (selection screen) statement.)
Listing 18.13 Explain the Sequence of Events That Occurs in this Program
report ztx1813 no standard page heading.
ztx1813 data: flag,
      ctr type i.
parameters p1.
initialization.
flag = 'I'.
write: / 'in Initialization'.
start-of-selection.
flag = 'S'.
write: / 'in Start-Of-Selection',
         / 'p1 =', p1.
top-of-page.
   add 1 to ctr.
   write: / 'Top of page, flag =', flag, 'ctr =', ctr.
   uline.
4) can anybody please mail me some exercise program queries ( right from the basic to complex one) on this mail id [email protected] or else u can give me the url of the website which contains such program.
EARGERLY WAITING FOR UR REPLIES
Regards,
maqsood

Maqsood,
I had tested all your programs and I am getting the correct output. I didnt get any error message and I didnt do any changes. I just copied your code and executed it.
To your Q3, I can say...INITIALIZATION is used only to assign values to variables. It is not used for output.
Only the start-of-selection and top-of-page will be printed.

Why do we need to distributed computing?

Hi all,
Why do we need distribute objects and what are the major advantages that this approach offer us?
Thanks.

Look up on the web; the 10 misconceptions of distributed programming; I haven't got time to find it in my data now. But it still fails to mention this one and only utterly important question; how many CPU cycles must a process miss before it becomes affordable to sacrifice even more CPU cycles to set up a TCP/IP connection to marshall every aspect of your call, send it to the other side and process the response in the reverse order ? Answer: a whole lot of CPU cycles. If the time it took to process the thing locally is smaller than the time it takes to set up the whole thing to work accross a network, then forget about it completely. You can't beat it. Not to mention that if your front-end is so busy that it needs a back-end to do some things, then the bandwidth it's going to need is usually so big, that the boxes should normally not be more than a slight distance apart, so there goes the argument for using it to address specialized services (which are usually not around the corner).

Design of first distributed architecture

Okay, so I'm trying to design and implement my first distributed project, and I want to make sure my general design is okay before I start. Like I say, I've never used J2EE before, and I'm still learning about it. This is very general.
Problem: Design a login system complete with the following aspects:
- A basic login window/applet that takes a username and password and verifies them. If they are valid (as determined by specific business logic), return a cookie (assume they are allowed for now) and allow the user access to the requested resources on the server. (Note: I think I'm using the term business logic correctly, but tell me if I'm not.)
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So that is my basic skeleton, but I have no idea as to its quality. What do you think?
theAmerican

_dnoyeB said:
An EJB per table seems odd. You should consider some
form of ORM. Perhaps EJB3 will work for you. As I
understand it, and its beena while since i did j2ee,
EJB represents a thing, not a databaase table. i.e.
an EJB represents a person, not the person table.Okay, that makes sense. (The idea of one EJB/table didn't seem exactly right to me.) By ORM, you mean something like Hibernate or EJB3? (Could Spring be involved here? I know it isn't solely concerned with DBs.) I appreciate the advice.
Saish said:
I would also consider implementing an out-of-the-box controller
ala Struts or Spring rather than dozens of Servlets. I was thinking about using Spring. Would you recommend doing that before I even do my first distributed app? Also, which do you prefer: Struts or Spring? Thanks for the input.
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If you are using J2EE I would suggest you read up on the security services
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setting up realms etc and also provide components to access security data
in order to perform authentication and authorisation etc.
Unless you have need for extended security you will probably find that the
containers services means you wont need to write your own components e.g.
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theAmerican

Program Manager

I am trying to write a distributed programming framework for Java - I suppose it is really P2P although nobody can seem to decide what exactly P2P is!
So far I have made a few design decisions that need to be checked and raise a few questions that need answering before i proceed.
I will have a main program running on every node in the dist/P2P network. This will do all the communication stuff. The main program will also be responsible for managing services on that node. For example I will have a computing service (think SETI et all).
Now the first problem. Say this node is capable of hosting an arbitrary service (either transmitted to it or run by the user). I do not want to have to recompile the whole damn thing to incorporate this service thereby interrupting the program.
What are my options:-
a) If a class file is placed into the corrrect directory and extends runnable and I am aware of the name of the class is it possible to run it and then add it to the thread manager.
b)????
Any problems with my above hopeful idea. Obvioulsy any other ideas and advice on any aspect will be greatly apreciated.

a) If a class file is placed into the corrrect
directory and extends runnable and I am aware of the
name of the class is it possible to run it and then
add it to the thread manager.Yes.
Do a search on "dynamic class loading". This topic has been discussed here many times before.
The basic principle is to use class loaders (usually java.net.URLClassLoader) to load the classes (and later let them be garbage collected if needed).
- Marcus

Powershell script assistance - adding another property to existing script

This is not my script but was written by Richard L. Mueller. It works perfectly for us but I would like to know if the account is enabled or disabled when the output is created. Basically it would output the name, lastlogon and then either enabled or disabled.
I've attempted to add a new property by adding another " $Searcher.PropertiesToLoad.Add" and "$Result.Properties.Item ".
It works fine if I add something like "givenName" but I can't find the property name to show if the account is enabled or disabled.
The entire script is shown below:
# PSLastLogon.ps1
# PowerShell script to determine when each user in the domain last
# logged on.
# Copyright (c) 2011 Richard L. Mueller
# Hilltop Lab web site - http://www.rlmueller.net
# Version 1.0 - March 16, 2011
# This program queries every Domain Controller in the domain to find the
# largest (latest) value of the lastLogon attribute for each user. The
# last logon dates for each user are converted into local time. The
# times are adjusted for daylight savings time, as presently configured.
# You have a royalty-free right to use, modify, reproduce, and
# distribute this script file in any way you find useful, provided that
# you agree that the copyright owner above has no warranty, obligations,
# or liability for such use.
Trap {"Error: $_"; Break;}
$D = [System.DirectoryServices.ActiveDirectory.Domain]::GetCurrentDomain()
$Domain = [ADSI]"LDAP://$D"
$Searcher = New-Object System.DirectoryServices.DirectorySearcher
$Searcher.PageSize = 200
$Searcher.SearchScope = "subtree"
$Searcher.Filter = "(&(objectCategory=person)(objectClass=user))"
$Searcher.PropertiesToLoad.Add("distinguishedName") > $Null
$Searcher.PropertiesToLoad.Add("lastLogon") > $Null
# Create hash table of users and their last logon dates.
$arrUsers = @{}
# Enumerate all Domain Controllers.
ForEach ($DC In $D.DomainControllers)
$Server = $DC.Name
$Searcher.SearchRoot = "LDAP://$Server/" + $Domain.distinguishedName
$Results = $Searcher.FindAll()
ForEach ($Result In $Results)
$DN = $Result.Properties.Item("distinguishedName")
$LL = $Result.Properties.Item("lastLogon")
If ($LL.Count -eq 0)
$Last = [DateTime]0
Else
$Last = [DateTime]$LL.Item(0)
If ($Last -eq 0)
$LastLogon = $Last.AddYears(1600)
Else
$LastLogon = $Last.AddYears(1600).ToLocalTime()
If ($arrUsers.ContainsKey("$DN"))
If ($LastLogon -gt $arrUsers["$DN"])
$arrUsers["$DN"] = $LastLogon
Else
$arrUsers.Add("$DN", $LastLogon)
# Output latest last logon date for each user.
$Users = $arrUsers.Keys
ForEach ($DN In $Users)
$Date = $arrUsers["$DN"]
"$DN;$Date"

It is part of the userAccountControl attribute. Retrieve that attribute for each user and test if the ADS_UF_ACCOUNTDISABLE bit (2) is set.
-- Bill Stewart [Bill_Stewart]

Database & DSN connection

Hi!
I use access database in my program and for that i'm setteling a connection to dsn in control panel. if i want to use my program in a site on the net, how can i connect the program to the database, cause that connection is only for the current computer?
Tahnx!

First write a Java program that successfully connects to the Access database locally and does the sort of thing you want to do with it (run queries, presumably). Then read some tutorials or articles on distributed programming to figure out how you want to connect to the server from the client based on your needs. Could be RMI, CORBA, web services, a servlet...

Is there a way to save comments into a "macro" or easily accessible file for quick/easy insertion?

To preface, I'm a lawyer and I use acrobat predominantly for its drawing and commenting features to "mark-up" contracts. I get scanned text documents, I resize them using "Edit Object" or print-to-PDF at a reduced size and then I draw on them and use the text callout bubbles.
As many of these contracts feature similar provisions, I often find myself making the same comments over and over, and I was wondering if anyone had a good method, or macro for inserting comments easily.
I was thinking of creating a blank PDF document and then copy-pasting each callout text box into the document under the respective heading, and creating Tags, but this seems awfully labor intensive.
Two other things:
1) Why doesn't Acrobat X Pro grant me an automated function/action to resize (using Edit Object) every page?
2) Acrobat needs better commenting tools for comments intended for printing. Most people in my industry don't have/know how to use Acrobat, so pop-up comments become either obtrusive (covering text) or confusing.

You could create a menu item or tool bar button to allow you to selected a comment from a pop-up menu.
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Automating Placement of Annotations by Thom Parker
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> 1) Why doesn't Acrobat X Pro grant me an automated function/action to resize (using Edit Object) every page?
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> 2) Acrobat needs better commenting tools for comments intended for printing. Most people in my industry don't have/know how to use Acrobat, so pop-up comments become either obtrusive (covering text) or confusing.
Acrobat was not designed for Attorneys. Better yet why do not attorneys learn how to use the tools they need to use to do their job or get proper technical support. This reminds me of the federal judge who felt PDF and Acrobat/Reader were too much trouble and she demanded all documents sent to her needed to be in the MS Word format. And when the attorneys complied with her order, she could not open the documents since she only had WordPerfect on her system with no conversion tools for MS Word documents.
You can use the text comment box tool or the call out tool to make comments that are not in a pop-up balloon.

Unable to create temporary backing file

My program is throwing out the error:
temporary open: /var/tmp/BDB20825: Too many open files
unable to create temporary backing file
This happens after my program has been running for about 4 hours. The program appears to run out of file descriptors. The listing of /proc/<PID>/fd shows hundreds of lines naming the same file (/var/tmp/BDB20825), like this:
lrwx------ 1 zobell users 64 Jul 28 14:41 622 -> /var/tmp/BDB20825 (deleted)
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The program repeats this error slowly, and is stuck inside the db code. Here is the gdb backtrace I am seeing every time I interrupt:
(gdb) where
#0 0x00e74410 in __kernel_vsyscall ()
#1 0x003d51dd in ___newselect_nocancel () from /lib/libc.so.6
#2 0x002e5d39 in __os_sleep () from /devel/tfm/external/RH4_32/dbxml/latest/install/lib/libdb-4.6.so
#3 0x002e43f1 in __os_openhandle () from /devel/tfm/external/RH4_32/dbxml/latest/install/lib/libdb-4.6.so
#4 0x002e52ad in __os_open () from /devel/tfm/external/RH4_32/dbxml/latest/install/lib/libdb-4.6.so
#5 0x002c0357 in __db_tmp_open () from /devel/tfm/external/RH4_32/dbxml/latest/install/lib/libdb-4.6.so
#6 0x002c006c in __db_appname () from /devel/tfm/external/RH4_32/dbxml/latest/install/lib/libdb-4.6.so
#7 0x002d50c9 in __memp_bhwrite () from /devel/tfm/external/RH4_32/dbxml/latest/install/lib/libdb-4.6.so
#8 0x002d4a27 in __memp_alloc () from /devel/tfm/external/RH4_32/dbxml/latest/install/lib/libdb-4.6.so
#9 0x002d62ec in __memp_fget () from /devel/tfm/external/RH4_32/dbxml/latest/install/lib/libdb-4.6.so
#10 0x00232003 in __bam_new_file () from /devel/tfm/external/RH4_32/dbxml/latest/install/lib/libdb-4.6.so
#11 0x002abc79 in __db_new_file () from /devel/tfm/external/RH4_32/dbxml/latest/install/lib/libdb-4.6.so
#12 0x002abaff in __db_open () from /devel/tfm/external/RH4_32/dbxml/latest/install/lib/libdb-4.6.so
#13 0x002a5d15 in __db_open_pp () from /devel/tfm/external/RH4_32/dbxml/latest/install/lib/libdb-4.6.so
#14 0x0080644c in Db::open () from /devel/tfm/external/RH4_32/dbxml/latest/install/lib/libdb_cxx-4.6.so
#15 0x0053ebbe in DbXml::DbWrapper::open (this=0x405bbee0, txn=0x0, type=DB_BTREE, flags=65537, mode=0) at Transaction.hpp:62
#16 0x00549247 in CacheDatabase (this=0x405bbed8, env=0x9c5a848, type=DB_BTREE, compare=0) at CacheDatabase.cpp:28
#17 0x005497e2 in DocDatabase (this=0x405bbed8, env=0x9c5a848, compare=0) at CacheDatabase.cpp:46
#18 0x00584ced in DbXml::Manager::createDocDatabase (this=0x9c5a830, compare=0) at Manager.cpp:694
#19 0x00519467 in DbXml::CacheDatabaseMinderImpl::verify (this=0xfffffdfe, entry=@0x6ac2f790, cid=-514) at CacheDatabaseMinder.hpp:31
#20 0x00519398 in DbXml::CacheDatabaseMinderImpl::findOrAllocate (this=0x6ac5b4f0, cid=1, allocate=true) at CacheDatabaseMinder.cpp:71
#21 0x00518e59 in DbXml::CacheDatabaseMinder::findOrAllocate (this=0x6acd9fa0, mgr=@0x9c5a830, cid=1, allocate=true) at CacheDatabaseMinder.cpp:21
#22 0x0055b12d in LazyDIResults (this=0x6acd9f98, context=0x6acd9fa0, contextItem=0x4979abc0, expr=@0x9ce5de8, txn=0x0, flags=0) at /devel/tfm/developers/szobell/berkeley-db-xml/dbxml-2.4.16/dbxml/include/dbxml/XmlManager.hpp:80
#23 0x0052f9cd in DbXml::QueryExpression::execute (this=0x9ce5de8, txn=0x0, contextItem=0x4979abc0, context=@0xbfcb0e04, flags=0) at /devel/tfm/developers/szobell/berkeley-db-xml/dbxml-2.4.16/dbxml/include/dbxml/XmlQueryContext.hpp:86
#24 0x00565a3a in DbXml::XmlQueryExpression::execute (this=0x0, contextItem=@0xfffffdfe, context=@0xbfcb0e04, flags=4294966782) at /devel/tfm/developers/szobell/berkeley-db-xml/dbxml-2.4.16/dbxml/include/dbxml/XmlValue.hpp:186
#25 0x0805af4b in XmlRecordWithCounts::ExtractQueryString (this=0xbfcb0dd0, select=@0xbfcb0e2c, result=@0xbfcac1d0, qDocument=0xbfcb0e14) at src/XmlRecordWithCounts.cpp:401
#26 0x080585f6 in OdRecord::GetRequiredContent (this=0xbfcb0dd0, name=@0xbfcac1e0, origin=@0xbfcac1d0, dest=@0xbfcac1c0, type=@0xbfcac1b0, dist=@0xbfcac198, totalCount=@0xbfcac194, route=@0xbfcac1a0, qDocument=0x0) at src/OdRecord.cpp:143
#27 0x0804d9c3 in ProcessOd (fpPrivate=0x8e11098, odDb=@0xbfcb0dd0, fdDb=@0xbfcb0d20) at src/BuildFdDb.cpp:263
#28 0x0804f4c8 in ProcessOneDest (fpPrivate=0x8e11098, odDb=@0xbfcb0dd0, fdDb=@0xbfcb0d20, dest={static npos = 4294967295, _M_dataplus = {<std::allocator<char>> = {<No data fields>}, Mp = 0x9da758c "LAX"}, static Sempty_rep_storage = {0, 0, 69041, 0}}) at src/BuildFdDb.cpp:464
#29 0x080501cd in main (argc=6, argv=0xbfcb10c4) at src/BuildFdDb.cpp:589
At this time, the program is trying to extract fields out of an XmlDocument that is the result of a query. The program uses a pre-calculated XmlQueryExpression to extract a specific field. This may not be the best way to extract a field from a document, given the apparent overhead of needing a temporary file!
My program queries two database files (OD.dbxml and FD.dbxml.new), and uses the information to add records to the second file. The databases are rather big:
bash-3.2$ ls -l /tmp/*dbxml*
-rw-rw---- 1 zobell users 5233745920 Jul 28 14:42 /tmp/FD.dbxml.new
-rw-rw---- 1 zobell users 6539427840 Jul 13 10:16 /tmp/OD.dbxml
(I keep them in /tmp because everywhere else uses NFS and performance is awful with NFS.)
My environment:
Red Hat Enterprise Linux Client release 5.3 (Tikanga) 32 bit.
Berkeley DB XML 2.4.16, C++ interface.
Disk space should not be an issue:
bash-3.2$ df /tmp /var
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/mapper/VolGroup00-tmp
28948572 13044384 14409968 48% /tmp
/dev/mapper/VolGroup00-root
144742920 5333544 131938272 4% /
I ran this program about a year ago and did not see this issue. I have made a few changes and linked to the newer version of the XML database since then. Any help is appreciated.

I have more information about this problem.
If I "disable" the routine __os_zerofill() in os_fzero.c, by having it always return (0), I no longer get an exception and my application appears to run smoothly. However, I have not determined what in this routine leads to the exception. And, I have no idea what the short and long term consequences of "disabling" this routine will be....
-Coralie

Use more than 2 GB ram for oracle

I have 16 GB ram but I only can use 2 GB of that for oracle database , how can i increase that ???

Don't merely go for increasing the size for Oracle (SGA) Memory. You need to keep collect the usage/statistics of your Oracle SGA, for any contention/or slow performance.
Until and unless users/clients reports that their reports/programs/queries are running slow, then think of increasing memory for Oracle. Moreover, instead of anticipating that the user reports the problem, you from your side need to check the hits of the memory allocated for Oracle.
By the way, you didn't specify your Database Version and OS Details.
If assumed, you are on Oracle 10g, then please take a look at the below Oracle Documentations links.
http://download.oracle.com/docs/cd/B19306_01/server.102/b14231/create.htm#ADMIN00207
Regards,
Sabdar Syed.

Java/java and java/c++ connection

Hello,
I'm new in distributed programming. Now I have to make a java application which can communicate with an other java and a c++ application. All of the 3 applications have to be made by me so I can controll all of the codes. All applications will run on the same machine.
The main java application only have to send an SQL statement to the 2. java and to the c++ application. The 2. java and the c++ application have to send back only a resultset.
Maybe it is not the best architecture, but it must do it in this way.
How can I start with it?
Any tutorial/example?

There is a "custom networking" tutorial on Sun's site. Or google for java socket tutorial for some others. The tutorials have sample servers and clients, grab one and extend it to build your own protocol.
I'd try to make the protocol line-oriented if possible (send text lines instead of "binary" data); avoids byte order and related problems, easier for inter-language work, and makes debugging easier.

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