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  • UnauthorizedAccessException when running desktop application from shared folder

    - by Atara
    I created a desktop application using VS 2008. When I run it locally, all works well. I shared my output folder (WITHOUT allowing network users to change my files) and ran my exe from another Vista computer on our intranet. When running the shared exe, I receive "System.UnauthorizedAccessException" when trying to read a file. How can I give permission to allow reading the file? Should I change the code? Should I grant permission to the application\folder on the Vista computer? how? Notes: I do not use ClickOnce. the application should be distributed using xcopy. My application target framework is ".Net Framework 2.0" On the Vista computer, "controlPanel | UninstallOrChangePrograms" it says it has "Microsoft .Net Framework 3.5 SP1" I also tried to map the folder drive, but got the same errors, only now the fileName is "T:\my.ocx" ' ---------------------------------------------------------------------- ' my code: Dim src As String = mcGlobals.cmcFiles.mcGetFileNameOcx() Dim ioStream As New System.IO.FileStream(src, IO.FileMode.Open) ' ---------------------------------------------------------------------- Public Shared Function mcGetFileNameOcx() As String ' ---------------------------------------------------------------------- Dim dirName As String = Application.StartupPath & "\" Dim sFiles() As String = System.IO.Directory.GetFiles(dirName, "*.ocx") Dim i As Integer For i = 0 To UBound(sFiles) Debug.WriteLine(System.IO.Path.GetFullPath(sFiles(i))) ' if found any - return the first: Return System.IO.Path.GetFullPath(sFiles(i)) Next Return "" End Function ' ---------------------------------------------------------------------- ' The Exception I receive: System.UnauthorizedAccessException: Access to the path '\\computerName\sharedFolderName\my.ocx' is denied. at System.IO._Error(Int32 errorCode, String maybeFullPath) at System.IO.FileStream.Init(...) at System.IO.FileStream..ctor(...) at System.IO.FileStream..ctor(String path, FileMode mode) ' ----------------------------------------------------------------------

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  • OSX - User home directories shared via NFS

    - by Hugh
    Hi, I've run into some problems with how I've got user home directories set up on our system here. Our server is an XServe, using Open Directory to manage the user accounts. The majority of our workstations are OSX, but there are a few running Linux (Centos 5.3), and, as time goes on, we expect the proportion of Linux workstations to increase (at some point, we expect to move the server side over to Linux too, but for now we're running with what we've already got) To ensure that the Linux and OSX workstations both see user's home directories in the same place, I shared the home directories using NFS. On the server end, the home directories are stored in: /Volumes/data/company_users This is mounted on the workstations to: /mount/company_users This work fine on the Linux workstations, but there is some weirdness under OSX. For the user who is logged in through the GUI, it all works just fine. However, if a user tries to SSH into a machine that they are not the primary user on, they often have no access to their own home directory. It looks as though OSX is trying to do something else to the user home directories mount point when you log in through the GUI.... For example, on this machine (nv001), I (hugh) am logged into the GUI. Last login: Mon Mar 8 18:17:52 on ttys011 [nv001:~] hugh% ls -al /mount/company_users total 40 drwxrwxrwx 26 hugh wheel 840 27 Jan 19:09 . drwxr-xr-x 6 admin admin 204 19 Dec 18:36 .. drwx------+ 128 hugh staff 4308 27 Feb 23:36 hugh drwx------+ 26 matt staff 840 4 Dec 14:14 matt [nv001:~] hugh% So Matt's home directory is accessible to him. However, if I try to switch to him: [nv001:~] hugh% su - matt Password: su: no directory [nv001:~] hugh% Or: [nv001:~] hugh% su matt Password: tcsh: Permission denied tcsh: Trying to start from "/mount/company_users/matt" tcsh: Trying to start from "/" [nv001:/] matt% Does anyone have any idea why it might be doing this? It's causing me all sorts of problems at the moment... The only machine that I can successfully switch users at the moment is the server that the user directories are stored on, where /mount/company_users is actually just a symlink to /Volumes/data/company_users Thanks

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  • SIM to OIM Migration: A How-to Guide to Avoid Costly Mistakes (SDG Corporation)

    - by Darin Pendergraft
    In the fall of 2012, Oracle launched a major upgrade to its IDM portfolio: the 11gR2 release.  11gR2 had four major focus areas: More simplified and customizable user experience Support for cloud, mobile, and social applications Extreme scalability Clear upgrade path For SUN migration customers, it is critical to develop and execute a clearly defined plan prior to beginning this process.  The plan should include initiation and discovery, assessment and analysis, future state architecture, review and collaboration, and gap analysis.  To help better understand your upgrade choices, SDG, an Oracle partner has developed a series of three whitepapers focused on SUN Identity Manager (SIM) to Oracle Identity Manager (OIM) migration. In the second of this series on SUN Identity Manager (SIM) to Oracle Identity Manager (OIM) migration, Santosh Kumar Singh from SDG  discusses the proper steps that should be taken during the planning-to-post implementation phases to ensure a smooth transition from SIM to OIM. Read the whitepaper for Part 2: Download Part 2 from SDGC.com In the last of this series of white papers, Santosh will talk about Identity and Access Management best practices and how these need to be considered when going through with an OIM migration. If you have not taken the opportunity, please read the first in this series which discusses the Migration Approach, Methodology, and Tools for you to consider when planning a migration from SIM to OIM. Read the white paper for part 1: Download Part 1 from SDGC.com About the Author: Santosh Kumar Singh Identity and Access Management (IAM) Practice Leader Santosh, in his capacity as SDG Identity and Access Management (IAM) Practice Leader, has direct senior management responsibility for the firm's strategy, planning, competency building, and engagement deliverance for this Practice. He brings over 12+ years of extensive IT, business, and project management and delivery experience, primarily within enterprise directory, single sign-on (SSO) application, and federated identity services, provisioning solutions, role and password management, and security audit and enterprise blueprint. Santosh possesses strong architecture and implementation expertise in all areas within these technologies and has repeatedly lead teams in successfully deploying complex technical solutions. About SDG: SDG Corporation empowers forward thinking companies to strategize their future, realize their vision, and minimize their IT risk. SDG distinguishes itself by offering flexible business models to fit their clients’ needs; faster time-to-market with its pre-built solutions and frameworks; a broad-based foundation of domain experts, and deep program management expertise. (www.sdgc.com)

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  • Mac OS X - User home directories shared via NFS

    - by Hugh
    I've run into some problems with how I've got user home directories set up on our system here. Our server is an XServe, using Open Directory to manage the user accounts. The majority of our workstations are OS X, but there are a few running Linux (Centos 5.3), and, as time goes on, we expect the proportion of Linux workstations to increase (at some point, we expect to move the server side over to Linux too, but for now we're running with what we've already got) To ensure that the Linux and OS X workstations both see user's home directories in the same place, I shared the home directories using NFS. On the server end, the home directories are stored in: /Volumes/data/company_users This is mounted on the workstations to: /mount/company_users This work fine on the Linux workstations, but there is some weirdness under OS X. For the user who is logged in through the GUI, it all works just fine. However, if a user tries to SSH into a machine that they are not the primary user on, they often have no access to their own home directory. It looks as though OS X is trying to do something else to the user home directories mount point when you log in through the GUI.... For example, on this machine (nv001), I (hugh) am logged into the GUI. Last login: Mon Mar 8 18:17:52 on ttys011 [nv001:~] hugh% ls -al /mount/company_users total 40 drwxrwxrwx 26 hugh wheel 840 27 Jan 19:09 . drwxr-xr-x 6 admin admin 204 19 Dec 18:36 .. drwx------+ 128 hugh staff 4308 27 Feb 23:36 hugh drwx------+ 26 matt staff 840 4 Dec 14:14 matt [nv001:~] hugh% So Matt's home directory is accessible to him. However, if I try to switch to him: [nv001:~] hugh% su - matt Password: su: no directory [nv001:~] hugh% Or: [nv001:~] hugh% su matt Password: tcsh: Permission denied tcsh: Trying to start from "/mount/company_users/matt" tcsh: Trying to start from "/" [nv001:/] matt% Does anyone have any idea why it might be doing this? It's causing me all sorts of problems at the moment... The only machine that I can successfully switch users at the moment is the server that the user directories are stored on, where /mount/company_users is actually just a symlink to /Volumes/data/company_users

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  • How To Block Web Sites at the Router Level for Network Wide Filtering

    - by Jason Fitzpatrick
    A comprehensive network filtering system is overkill if all you want to do is block a handful of web sites. Read on as we show you how—with nothing more than your router—you can selectively block and temporarily restrict individual websites. For many people a massive commercial internet filter is overkill. What if you just want to block Facebook when your kids are supposed to be doing their homework or Reddit when you’re supposed to be getting work done? You don’t need a huge system for that, all you need is the access restrictions module in your router. Today we’re looking at how you can quickly and easily block traffic on your network using router-based access restrictions. HTG Explains: When Do You Need to Update Your Drivers? How to Make the Kindle Fire Silk Browser *Actually* Fast! Amazon’s New Kindle Fire Tablet: the How-To Geek Review

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  • Configuring OS X L2TP VPN to use Certificate for IPSEC layer instead of Pre Shared Key

    - by Matthew Savage
    I'm trying to setup a L2TP VPN on an OS X Snow Leopard Server setup, and have had success using a pre-shared key, however I would rather not rely on a simple string, and use a certificate instead. Setting this up on the server side is seemingly easy, you simply select a certificate you have generated from the list, and hit apply, however when I try to use the certificate on the client side it fails. I have exported the certificate into a P12 file, and then transferred to the client, and imported into the login keychain, however when I try to choose the certificate (from Network preferences, clicking Authentication Settings, then selecting Certificate and pressing Select) I am shown the following error: No machine certificates found Certificate authentication cannot be used because your keychain does not contain any suitable certificates. Use Keychain Access to import the certificate into your keychain. If you do not have the certificates required for authentication, contact your network administrator. Unfortunately even when I try to generate a certificate where I override the defaults, ensure the DNS name etc are set properly this doesn't change. When I select Certificate Authentication for the User Auth, and click Select the certificate for the server shows up there, but obviously this isn't where I need it to be available.

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  • Refactoring an immediate drawing function into VBO, access violation error

    - by Alex
    I have a MD2 model loader, I am trying to substitute its immediate drawing function with a Vertex Buffer Object one.... I am getting a really annoying access violation reading error and I can't figure out why, but mostly I'd like an opinion as to whether this looks correct (never used VBOs before). This is the original function (that compiles ok) which calculates the keyframe and draws at the same time: glBegin(GL_TRIANGLES); for(int i = 0; i < numTriangles; i++) { MD2Triangle* triangle = triangles + i; for(int j = 0; j < 3; j++) { MD2Vertex* v1 = frame1->vertices + triangle->vertices[j]; MD2Vertex* v2 = frame2->vertices + triangle->vertices[j]; Vec3f pos = v1->pos * (1 - frac) + v2->pos * frac; Vec3f normal = v1->normal * (1 - frac) + v2->normal * frac; if (normal[0] == 0 && normal[1] == 0 && normal[2] == 0) { normal = Vec3f(0, 0, 1); } glNormal3f(normal[0], normal[1], normal[2]); MD2TexCoord* texCoord = texCoords + triangle->texCoords[j]; glTexCoord2f(texCoord->texCoordX, texCoord->texCoordY); glVertex3f(pos[0], pos[1], pos[2]); } } glEnd(); What I'd like to do is to calculate all positions before hand, store them in a Vertex array and then draw them. This is what I am trying to replace it with (in the exact same part of the program) int vCount = 0; for(int i = 0; i < numTriangles; i++) { MD2Triangle* triangle = triangles + i; for(int j = 0; j < 3; j++) { MD2Vertex* v1 = frame1->vertices + triangle->vertices[j]; MD2Vertex* v2 = frame2->vertices + triangle->vertices[j]; Vec3f pos = v1->pos * (1 - frac) + v2->pos * frac; Vec3f normal = v1->normal * (1 - frac) + v2->normal * frac; if (normal[0] == 0 && normal[1] == 0 && normal[2] == 0) { normal = Vec3f(0, 0, 1); } indices[vCount] = normal[0]; vCount++; indices[vCount] = normal[1]; vCount++; indices[vCount] = normal[2]; vCount++; MD2TexCoord* texCoord = texCoords + triangle->texCoords[j]; indices[vCount] = texCoord->texCoordX; vCount++; indices[vCount] = texCoord->texCoordY; vCount++; indices[vCount] = pos[0]; vCount++; indices[vCount] = pos[1]; vCount++; indices[vCount] = pos[2]; vCount++; } } totalVertices = vCount; glEnableClientState(GL_NORMAL_ARRAY); glEnableClientState(GL_TEXTURE_COORD_ARRAY); glEnableClientState(GL_VERTEX_ARRAY); glNormalPointer(GL_FLOAT, 0, indices); glTexCoordPointer(2, GL_FLOAT, sizeof(float)*3, indices); glVertexPointer(3, GL_FLOAT, sizeof(float)*5, indices); glDrawElements(GL_TRIANGLES, totalVertices, GL_UNSIGNED_BYTE, indices); glDisableClientState(GL_VERTEX_ARRAY); // disable vertex arrays glEnableClientState(GL_TEXTURE_COORD_ARRAY); glDisableClientState(GL_NORMAL_ARRAY); First of all, does it look right? Second, I get access violation error "Unhandled exception at 0x01455626 in Graphics_template_1.exe: 0xC0000005: Access violation reading location 0xed5243c0" pointing at line 7 Vec3f pos = v1->pos * (1 - frac) + v2->pos * frac; where the two Vs seems to have no value in the debugger.... Till this point the function behaves in exactly the same way as the one above, I don't understand why this happens? Thanks for any help you may be able to provide!

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  • locked files on HFS+ home partition shared between OSX/Linux

    - by HazyBlueDot
    I dual boot into Arch Linux and OS X 10.6 on my MacBook pro. I synced my UID between both OSes and created an HFS partition (with no journaling) to use as a shared home/Users partition. For the most part it works just as I'd expect, but sometimes when I'm booted into OS X certain files are "locked" (when I get info on a particular file the "Locked" box is checked under the "General" pane. I can resolve the issue by manually unchecking the box) and/or I get "Operation not permitted" when I try deleting or chmod'ing a file. In both cases I don't see anything out of the ordinary on the permission bits displayed with ls -l, except for a trailing '@' character in the position where the sticky bit would normally occur: -rw-r--r--@ 1 myuser mygroup 296 Mar 29 11:44 myfile This '@' character shows up on ALL normal files, so doesn't seem to be linked to the locked/operation not permission situation. On the Linux side of things I never have permission problems. To the best of my limited knowledge and experience with ACLs I've not found any ACLs on any of the files in question. For what it's worth, I do most of my file editing using emacs (Aquamacs in OSX), is it possible it is setting weird permission bits? What is the "locked" setting that OS X uses and does it have a permission bit equivalent (so at the very least I could recursively unlock all files in my home directory from the terminal) why might some, but not other files get "locked" when booting into OS X what is the meaning of the '@' character?

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  • Very slow browsing shared folder XP client/host

    - by Ickster
    I have a pretty straightforward setup where I'm storing media files on an XP pro machine, and sharing the folder to be accessed by other XP pro machines around the house. (Typically, there's only one client accessing the share at a time, although there may be several with the share mounted.) It's been working just fine for years, but I've recently started having some problems. A couple of days ago, the host PC had power disconnected while it was running. It was restarted and everything seemed fine initially, but since then browsing the shared folder from client machines has been extremely slow and actually reading data is all but impossible. The problem exists in every access method I've tried: Windows Explorer, VLC dialogs, command line, etc. My first thought was that the disk was experiencing problems, but there are no problems viewing the files locally on the host machine. My second thought was that there was a network problem on the host machine, so I removed and reinstalled drivers for the NIC with no change. My third thought was that there might've been a problem elsewhere on the network, so I swapped out hardware to no avail. I'm regrouping and trying to come up with a methodical approach to figuring out what might be wrong. I would of course be thrilled if you can suggest specific problems (Microsoft KB articles, etc.) that I might check, but I'm not expecting a silver bullet. If you can help me outline an approach to identify the problem (including recommended tools, e.g., disk checkers, network analyzers, etc.) I'd greatly appreciate it.

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  • Shared printer hosted by Windows 7 to XP peers [closed]

    - by Alistair Knock
    Possible Duplicate: Add Network Printer drivers in Windows 7/Server 2008 R2? A Canon Pixma ip4600 installed all by itself when connected to a Windows 7-64 bit machine. I then updated it with the add-on Canon provide to give additional functionality. I then wish to share it with a box which is running Windows XP 32-bit. The XP box can see the printer but can't find a driver from the 7 machine, which is fine. I ask the 7 machine to get the x86 drivers, but it can't. I install the 32-bit XP drivers on the XP machine, but unlike previous Canon drivers (which unzip to give an .inf file), they assume a local printer and partially give up. I find the .inf file in the Program files\CanonBJ\... directory. Neither the XP machine, nor the 7 machine when the CanonBJ directory is shared to it, is happy with the .inf file. I attempt to install the 32-bit drivers on the 64-bit 7 machine, which, understandably, fail. Where do we go from here? (I apologise for posting in the first-person, I'm not sure why this was)

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  • Hybrid wireless network repeating

    - by Oli
    Summary: I'd like to use two Ubuntu computers to extend/compliment an existing wireless access point. I have a network which currently looks a bit like this: What the diagram doesn't show is the interference caused by our house. It's a wifi-blocking robot sent here from the past. The two wired computers are in areas where the signal is most blocked (not by design, just a happy co-incidence). Both wired computers have fairly good network cards. They're both Ubuntu machines and I would like to turn them into additional base stations. I know I could throw more networking hardware at this (network extenders or cable in additional, pure wireless access points) but I've got two Linux machines sitting in ideal places and I feel like they should be able to help me out. I've tried ad-hoc networks but I need something that is a lot more transparent (eg you can migrate from base to base without a connection dropping); it should look like one network to clients.

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  • What sort of security method is this called (if it has a name)?

    - by loosebruce
    I have thought of a way of securing access to an application interacting with another application. Using this method Application 1 - "What is the sum of 1+1?" Application 2 - "3" Application 1 - "Access granted" Is this method used a lot, does it have a classification in the programming world? The advantages for me of using this is that I do not have to spend more effort implementing security keys/certificates. Any unauthorized machine trying to interpret it would give the correct result and identify itself as untrusted. What sort of weaknesses are there to doing this?

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  • Shared Files stuck locked even after closing all sessions

    - by Chris S
    We run a business app from a shared network drive (has to be this way). When I go to do updates it complains that files are locked. Generally there are open sessions from people who left their computer on, but with no locks on files; there aren't necessarily always sessions open when it complains about locked files. If I close these sessions they disappear. I say "disappear" because I suspect they're actually hanging open. If I try to restart the Server service, it hangs on stopping. Restarting the whole server (it's a VM) unlocks the files. The Server is a Windows 2008 R2 Ent VM running on Hyper-V; the share is accessed through DFS. Offline Files and caching are disabled (Share and GPO). All clients are Win7. Nothing has SP1 yet. Any ideas on what causes the file locks to hang? Any ideas for a solution other than rebooting the server every time?

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  • How to setup a wifi ap hotspot with ipv6 support?

    - by keyman
    How to setup a wifi ap (access point mode) hotspot, with IPv6 support? I've set up a hotspot according to the guide to wifi ap hotspot setup and it works fine. But via the hotspot I failed to visit IPv6 websites. How can I setup a hotspot able to share Ipv6 Internet access? Thanks! Further: Actually I've tried to setup IPv6 forwarding and masquerading. First enabling IPv6 forwarding: echo 1 | sudo tee net/ipv6/conf/default/forwarding Then I tried to execute: sudo ip6tables -t nat -A POSTROUTING -s 2001:db8:0:1::/64 -o eth0 -j MASQUERADE But it gave me an error: ip6tables v1.4.12: Couldn't load target `MASQUERADE':No such file or directory I searched through the Internet but I get confused. So I'm here for help. Thanks!

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  • using remote MS Access database which connects to remote SQL server

    - by Manjot
    Hi, We have a Microsoft Access database + application (on Server A) which connects to a remote SQL server (Server B) using System DSN ODBC connection (on Server A) to the SQL database server. The users are open this Access database remotely as it is on a shared location on the server A. They still have to create a local ODBC connection on their computers to connect to Server B. Is there anyway that they can access the Access database and not have to create a local ODBC connection? thanks in advance

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  • How to access an IP address as if on a different network using SSH

    - by NT3RP
    In preparation for a lengthy business trip, I set up my router such that I can access my home computer over the internet via port forwarding over SSH. One thing I neglected to do was setup access to my router remotely. Normally, I can just access the router configuration page via 192.168.1.1. I know that it's possible to tunnel traffic through SSH, but how do I access an IP address as if I were on my home network using SSH?

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  • How can access files on shared drive from Windows 2008 server configured with SFTP

    - by communicator
    I have installed OpenSSH on my windows 2008 server by following the user guide here . Now I have some files on windows network share with UNC path as \\corp\test\testdata I want map this file system on network share to my windows 2008 server which is configred with SFTP so that I can access these files from my Java Program by doing SFTP to windows 2008 server.Is there anyway I can map the network share to C or other drive in server so that all the files on the share will be available as local files on the server?

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  • Controling virtualbox internet access?

    - by HandyGandy
    Host: Linux/Debian/Ubuntu/Mint ( Helena/karmic koala ) Guest: XP SP2 and SP3 Problem: Relatively new copy of XP migrated to vbox-virus free. To detect biral infection it is desired that internet access is limited. Network access to the host is desired, but access to the internet should be limited to a select few sites. The added overhead of network access should be small when the guest vbox is running, 0 when it is not.

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  • IIS 7 Web service access

    - by Aharon Manne
    I am trying to debug a simple web service. I have IIS 7 installed on my development machine (Windows 7), and have installed the web service. I can access it from my development machine, but not from any other machine in the local network.I opened the firewall to HTTP access, and I can access the default website from other machines, so it is not the firewall.What security settings should I look at to try to allow devices on the LAN to access the web service?

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  • httpd.conf ruined - can't access my vps anymore

    - by Jazerix
    Okay, so this may be incredible stupid But I was configuring my httpd.conf file yesterday. After a server restart, I can no longer access it. Port 80 is working fine, and it displays my webpages, however when I access the site via ssh, it just says the connection was refused. I cannot access webmin which is port 10000 or access it via ftp :/ Do I need to recreate the whole site or is there a way to get into it? I think I messed up the virtual hosts :)

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  • httpd.conf ruined - cant access my vps anymore

    - by Jazerix
    Okay, so this may be incredible stupied But I was configuring my httpd.conf file yesterday. After a server restart, I can no longer access it. Port 80 is working fine, and it displays my webpages, however when I access the site via ssh, it just says the connection was refused. I cannot access webmin which is port 10000 or access it via ftp :/ Do I need to recreate the whole site or is there a way to get into it?

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  • Can't change pivot table's Access data source - bug in Excel 2000 SP3?

    - by Ron West
    I have a set of Excel 2000 SP3 worksheets that have Pivot Tables that get data from an Access 2000 SP3 database created by a contractor who left our company. Unfortunately, he did all his work on his private area on the company (Novell) network and now that he has left us, the drive spec has been deleted and is invalid. We were able to get the database files restored to our network area by our IT Service Desk people, but we now have to re-link everything to point to our group area instead of the now-nonexistent private area. If I follow the advice given elsewhere on this site (open wizard, click 'Back' to get to 'Step 2 of 3', click 'Get Data...' I get a message that the old filespec is an invalid path and I need to check that the path name is invalid and that I am connected to the server on which the file resides. I then click on OK and get a Login dialog with a 'Database...' button on the right. I click this and get a 'Select Database' dialog which allows me to choose the appropriate database in its correct new location. I then click OK, which takes me back to the 'Login' screen. I can confirm that it has accepted my new location by clicking on 'Database...' as before and the NEW location is still shown. So far so good - but if I then click on OK I get two unhelpful messages - first I get one saying that Excel 'Could not use '|'; file already in use.' - although no other files are in use. Clicking on OK takes me back to the 'Login' dialog. Clicking OK again gives me the same message as before telling me that the OLD filespec is invalid (as if I hadn't changed anything) - but clicking on the 'Database...' button shows that the correct (NEW) database location is still selected. Can anyone tell me a way of using VBA to change the link information without having to spend hours fighting the PivotTable Wizard - preferably similar to this way you update an Access Tabledef:- db.TableDefs(strLinkName).Connect = strNewLink db.TableDefs(strLinkName).RefreshLink Thanks!

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  • Can you force a crash if a write occurs to a given memory location with finer than page granularity?

    - by Joseph Garvin
    I'm writing a program that for performance reasons uses shared memory (alternatives have been evaluated, and they are not fast enough for my task, so suggestions to not use it will be downvoted). In the shared memory region I am writing many structs of a fixed size. There is one program responsible for writing the structs into shared memory, and many clients that read from it. However, there is one member of each struct that clients need to write to (a reference count, which they will update atomically). All of the other members should be read only to the clients. Because clients need to change that one member, they can't map the shared memory region as read only. But they shouldn't be tinkering with the other members either, and since these programs are written in C++, memory corruption is possible. Ideally, it should be as difficult as possible for one client to crash another. I'm only worried about buggy clients, not malicious ones, so imperfect solutions are allowed. I can try to stop clients from overwriting by declaring the members in the header they use as const, but that won't prevent memory corruption (buffer overflows, bad casts, etc.) from overwriting. I can insert canaries, but then I have to constantly pay the cost of checking them. Instead of storing the reference count member directly, I could store a pointer to the actual data in a separate mapped write only page, while keeping the structs in read only mapped pages. This will work, the OS will force my application to crash if I try to write to the pointed to data, but indirect storage can be undesirable when trying to write lock free algorithms, because needing to follow another level of indirection can change whether something can be done atomically. Is there any way to mark smaller areas of memory such that writing them will cause your app to blow up? Some platforms have hardware watchpoints, and maybe I could activate one of those with inline assembly, but I'd be limited to only 4 at a time on 32-bit x86 and each one could only cover part of the struct because they're limited to 4 bytes. It'd also make my program painful to debug ;)

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  • How to pass parameters to manage_shared_memory.construct() in Boost.Interprocess

    - by recipriversexclusion
    I've stared at the Boost.Interprocess documentation for hours but still haven't been able to figure this out. In the doc, they have an example of creating a vector in shared memory like so: //Define an STL compatible allocator of ints that allocates from the managed_shared_memory. //This allocator will allow placing containers in the segment typedef allocator<int, managed_shared_memory::segment_manager> ShmemAllocator; //Alias a vector that uses the previous STL-like allocator so that allocates //its values from the segment typedef vector<int, ShmemAllocator> MyVector; int main(int argc, char *argv[]) { //Create a new segment with given name and size managed_shared_memory segment(create_only, "MySharedMemory", 65536); //Initialize shared memory STL-compatible allocator const ShmemAllocator alloc_inst (segment.get_segment_manager()); //Construct a vector named "MyVector" in shared memory with argument alloc_inst MyVector *myvector = segment.construct<MyVector>("MyVector")(alloc_inst); Now, I understand this. What I'm stuck is how to pass a second parameter to segment.construct() to specify the number of elements. The interprocess document gives the prototype for construct() as MyType *ptr = managed_memory_segment.construct<MyType>("Name") (par1, par2...); but when I try MyVector *myvector = segment.construct<MyVector>("MyVector")(100, alloc_inst); I get compilation errors. My questions are: Who actually gets passed the parameters par1, par2 from segment.construct, the constructor of the object, e.g. vector? My understanding is that the template allocator parameter is being passed. Is that correct? How can I add another parameter, in addition to alloc_inst that is required by the constructor of the object being created in shared memory? There's very little information other than the terse Boost docs on this.

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