The Question:
Is there some way to force close access so it doesn't need access to the back-end server in order to exit?
The Situation:
I have an Access 2016 DB. The back-end is on a networked share drive which is only accessible when connected to the lan or on VPN. On load there is a ping test to the server, if found it copies the tables to local tables, if not, it just tells the user can't connect and continues on using the old data. The users travel a lot and can't always be on the VPN so the idea is that the data they have isn't more than a few days old. BTW, did I mention the users are only consumers of information and not contributors so I don't care that they can't write to the back-end. The tables contain a few 100k records, the application just puts it in nice easy to search and cross-reference reports.
The Problem:
While this loads and runs really nicely regardless of them being connected to the lan or not, it will NOT close if they don't have a connection to the server. It doesn't produce an error which I could easily handle, it just hangs. Task Manager won't even close it.
Attempted Solutions:
I tried to unlink the tables and just use a temporary connection to the backend to load the tables when I need them at the beginning, however this meant the user was prompted by the Microsoft Trust Center about 8 times every single time they loaded this unless I have each of them actually open the back-end DB themselves, give them the password to do that, and none of that is practical.
Access doesn't play well with remote BE..if you want to be on the Remote Side with Access you have 2 options :
Connect via RDS..the user connects to the server via Remote Desktop ..everything is "local" ..so now issues on lost connections ...as long the RDP connection hold everything is smooth and more importantly you don't have BE disconnects that cause corruption or loosing data (hint : Using the RemoteApp technology it will seem to the end user like he/she is working locally...i am using it and its great)
Switch BE...as i said , is not wise to use Access BE via remote connection..in order to do that switching to MsSQL/MySQL/PostGre ...etc will give you the true remote connection capability
After playing with all the settings for a few days, I finally figured out what my problem was.
In an effort to test different settings to see if I could reduce file size at one point I turned on "clear cache on exit" in the Current Database settings. Turning this off fixed the problem. I had forgotten that was on, so it turned out to not be a programming issue after all.
Related
On a lot of public webpages, hosted by people at their own homes, they use their own desktops as webserver. Within this kind of setting usually I use a form of server sided language (like php) that connects to an MySQL server on the same machine. When installing this I always give an password to the “root” user and create a new user and password for the application (the php) script to use. Because both script and database are on the same “localhost” I always set the allowed connection to only allow connections from the local host and not from anywhere else. So both “root” and other “users” can only connect from when accessed from within the machine.
(the separate “root” and “user” accounts are made to give them separate privileges and an user can not drop scheme’s for example)
Today it struck me, why am I setting passwords in MySQL? Because if you want to connect to this database you already have to been logged in in the local machine. So, is setting passwords really necessary or just a redundant precaution?
And if it’s NOT an redundant precaution, why is it unsafe to not set a password.
(not that it is a big burden, but I have to remember all these passwords somehow, using encrypted systems this is not a real big problem, but if it could be avoided than……)
The comments on your post have mostly summed this up, but as far as I am aware, this is known as "Defense in depth" (See 1 and 2). Defense in depth is basically about avoiding having a single point of failure in your project - If your webserver is compromised, having a weak password means that you're just giving away your database for free. This would be equivalent to somebody breaking into your house to find you've placed your safe on the kitchen table and unlocked it.
If you're hosting an externally facing website that you hope to get a decent amount of traffic, making it as secure as possible is a good idea, unless you particularly like the idea of malicious users having direct access to your home network. That said, if you are expecting a decent amount of traffic I highly recommend hosting your website elsewhere - You may find that your home internet speeds suffer greatly as a result.
I am developing an application which uses as a back-end an MS Access database (.mdb, not my decision). Recently I came across someone suggesting that using JET engine over WAN is not really a good idea, with a high risk of data corruption. Since my application should be doing just that (connecting to database on NAS (EDIT: not NAS, shared shared network drive), I got worried. It is really that risky? If so, is there any work around or is an MS Access database just unusable for that kind of application?
EDIT
The front end is .NET windows desktop application in C# (WPF). The system does not have many users, max 10. Most of the time they will approach the database from LAN and 99% of writing to the database will be done within the LAN (from the area of the company). However there are some cases where they will connect to the NAS (EDIT: not NAS, shared shared network drive) from outside the company via network (from their home).
If you have a 100 Mb/s fibre, it will be OK, but if your line is, say, an xDSL line, it is generally an absolute no-no.
Convince the powers that be to move the backend to a server engine like SQL Server where the Express version is free.
The scenario you describe is not a good fit for having an Access database as the back-end. The WAN users could very well find the application slow, but the NAS is the real cause for concern regarding corruption, and that would affect both LAN and WAN users.
Many (most?) NAS devices run on Linux and use Samba to provide Windows file-sharing services. The Access Database Engine apparently uses some low-level features of "real" Windows file sharing that Samba does not always fully implement (ref: here).
In fact, the only time I've seen repeated corruption problems with a shared Access back-end (and a properly distributed front-end) was when a client moved their file shares from an older Windows server to a newer NAS device. The Access application continued to work for the most part, but every few months they would find that the primary keys of some tables would disappear after they did a Compact and Repair on the back-end database file. That never happened while their file share was on the Windows server.
Splitting a front-end from a back-end removes the majority of the risk of corruption. Of course, with Access there's always the possibility and if you're looking for something that reduces the risk to close to nil then you might want to consider SQL Server or MySQL. However, using Access is fine as long as you take proper precautions.
For example, you might want to look into record-locking on tables that will get edited, to prevent multiple simultaneous writes. Backing up your DB on a regular basis is always good, too.
I am currently using VB6 to connect to a MS access DB using DAO and I’m experiencing a very noticeable speed reduction when a 2nd user connects to the Database.
Here are the steps to reproduce:
Open the Database from computer A by logging into the software
Add records to the database via the software (takes about .4 seconds)
A second user logs into the software (Computer B), ie: this opens the database, displays todays transactions, but the user does nothing else
On Computer A, repeat the operation of adding records, now the operation takes approximately 6 seconds
Further info…
the operation continues to take aprox 6 seconds, even after Computer B logs out of the software
if you close and reopen the application from Computer A the operation returns to taking only .4 seconds to execute!
Any help would be greatly appreciated!
Thanks!
That is the way MS Access works. While it kind of supports multiple users, and kind of supports placing the DB on a file share so multiple PCs can access it, it does neither really well. And if you are doing both (multi-user and over a network to a file share) then I feel for your pain.
The answer is to run the upgrade wizard and convert this to an MS SQL Server instance. MS SQL Server Express edition is a good choice to replace Acess in the case. Note that you can still keep all of your code and reports etc you have in Access, only the data needs to be moved.
Just to be clear on the differences, in MS Access when you read data from the database, all of the data required to perform your query is read from a file by your program, no server-side processing is done. If that data resides on a network, you are pulling that data across your network. If there are multiple users, you have an additional overhead of locking. Each users program/process effectively dialogs with the program/process of the other users via file I/O (writing lock info into the networked file or files). And if the network I/O times out or has other issues then those files can become corrupted.
In SQL Server, it is the SQL Server engine that manages the data requests and only returns the data required. It also manages the locks and can detect when a client has disconnected or timed out to clean up, which reduces issues caused by multiple users on a network.
We had this problem with our VB3 / Jet DB 2.5 application when we transitioned to using newer file servers.
The problem is "opportunistic locking" : http://support.microsoft.com/kb/296264?wa=wsignin1.0
Albert is probably describing the same thing ; the server will permit one client exclusive access of a file, but when another chimes in, this exclusive access will "thrash" between them, causing delays as the client with the oplock flushes all it's local cache to the server before the other client can access the file.
This may also be why you're getting good performance with one client - if it takes an oplock, it can cache all the data locally.
This can also cause some nasty corruption if one of your clients has a power failure or drops off the network, because this flushing of the local cache to the server can be interrupted.
You used to be able to disable this (on the client - so you need to service ALL the clients) on Windows 2000 and XP as per the article, but after Vista SP2 it seems to be impossible.
The comments about not using Access / JetDB as a multi-user database are essentially correct - it's not a good architectural choice, especially in light of the above. DAO is also an obsolete library, even in the obsolete VB6. ADODB is a better choice for VB6, and should allow you some measure of database independence depending on how your app is written.
Since as you pointed out you get decent performance with one user on the system, then obviously your application by nature is not pulling too much data over the network, and we can't blame network speed here.
In fact what is occurring is the windows file share system is switching from single file share mode into multi-share file mode. This switching file modes causes a significant delay. And this also means that the 2nd or more user has to attempt to figure out and setup locks on the file.
To remove this noticable delay simply at the start of your application open what we call a persistent connection. A persistent connection is simply something that forces the network connection to remain open at all times, and therefore this significant delay in switching between two file modes for file share is eliminated. You now find that performance with two users should be the same as one (assuming one user is idle and not increasing network load). So at application startup time, open a back end table to a global var and KEEP that table open at all times.
So, we want to move out from Air (Adobe stopping support and really bad implementation for the sqlite api, among other things).
I want to make 3 things:
Connect with a flash (not web) application to a local mysql database.
Connect with a falsh (not web) application to a remote mysql database.
Connect with a flash (web) application with a remote mysql database.
All of this can be done without any problem, however:
1 and 2 can be done (WITHOUT using a webserver) using for example this:
http://code.google.com/p/assql/
3 can be done using also the above one as far as I understand.
Question are:
if you can connect with socket wit mysql server, why use a web server (for example with php) to connect like a inter connectioN? why not connnect directly?
I have done this a lot of times, using AMFPHP for example, but wouldn't be faster going directly?
In the case of accessing local machine, it will be a more simple deploy application that only require the flash application + mysql server, not need to also instal a web server.
Is this assumption correct?
Thanks a lot in advance.
The necessity of separate layer of data access usually stems from the way people build applications, the layered architecture, the distribution of the workload etc. SQL server usually don't provide very robust API for user management, session management etc. so one would use an intermediate layer between the database and the client application so that that layer could handle the issues not related directly to storing the data. Security plays a significant role here too. There are other concerns as well, as, for example, some times you would like to close all access to the database for maintenance reasons, but if you don't have any intermediate layer to notify the user about your intention, you'd leave them wondering about whether your application is still alive. The data access layer can also do a lot of caching, actually saving your trips to the database, you would have to make from client (of course, the client can do that too, but ymmv).
However, in some simple cases, having an intermediate layer is an overhead. More yet, I'd say that if you can, do it without an intermediate layer - less code makes better programs, but all chances are for that you will find yourself needing that layer for one reason or another.
Because connecting remotely over the internet poses huge huge huge security problems. You should never deploy an application that connects over the internet to a database directly. That's why AIR and Flex doesn't have remote Mysql Drivers because they should never be used except for building development type tools. And, even if you did build a tool that could connect directly, any descent network admin is going to block access to the database from anywhere outside the DMZ and internal network.
First in order your your application to connect to the database the database port has to exposed to the world. That means I won't have to hack your application to get your data. I just need to hack your database, and I can cut you out of the problem entirely because you were stupid enough to leave your database port open to me.
Second most databases don't encrypt credentials or data traveling over the wire. While most databases support SSL connections most people don't turn it on because applications want super fast data access and they don't want to pay for SSL encryption overhead blah blah blah. Furthermore, most applications sit in the DMZ and their database is behind a firewall so between the server and the database is unlikely something could be eavesdropping on their conversation. However, if you connected directly from an AIR app to the database it would be very easy to insert myself in the middle and watch the traffic coming out of your database because your not using SSL.
There are a whole host of problems doing what you are suggesting around privacy and data integrity that you can't guarantee by allowing a RIA direct access to the database its using.
Then there are some smaller nagging issues like if you want to do modern features like publishing reports to a central server so users don't have to install your software to see them, sending out email, social features, web service integration, cloud storage, collaboration or real time messaging etc you don't get if you don't use a web application. Middleware also gives you control over your database so you can pool connections to handle larger load. Using a web application brings more to the table than just security.
I work for a small company and they asked me to build a simple access database. They only have terminals in the office that I work in (Ottawa) while the server is in Toronto (windows server 2003). When I load Access 2007 the whole program is extremely slow compared to normal speeds of the terminal. Only when I am in any form of Design View does my Terminal speed up. My question is; is there a way to increase the "speed" of Access when I'm trying to build the database and secondly will this effect the end user once the database is built? (everyone uses terminals)
Thanks in advance.
The use of the word terminal can mean many things here, but it does sound like you have a decent setup that should be able to work with good performance.
Also, the fact that you suggest that when in design mode, the application seems to speed up suggests the use of what is called a persistent connection may very well solve your problem.
Given that you using some type of remote desktop technology here than in fact network speeds should not really come into play and slow down the operation of this application by any noticeable amount.
First of all if there's multiple users using this application, as a general rule you should split the database into two parts, a front end part, and a so called back end part. Because you using a terminal technology, then the front ends and back ends will remain on the server, but each individual user logging into the system could have their OWN copy of the front end.
The next thing to do is to check what call the persisting connection, and in fact access is quite sensitive to local network printers. In your case when a user logs into this terminal system, often a local printer is "created" that is part of your local terminal but you still running Access on the server and Access will attempt to "talk" to that local network printer. So this forces additional communication between Access on the server and your default printer which is local.
I would attempt to setting a default printer that is NOT local to your WorkStation, and see if that helps. There's also a great list of other things to check in terms of slowing down performance, and a great FAQ you want to look at is here:
http://www.granite.ab.ca/access/performancefaq.htm
In the above the persistent connection idea is also suggested.