I am working on migrating a MS Access Database over to a newer SQL platform.
But, with all of the users who are currently using it, we're migrating slowly/carefully.
The first step is that we are re-writing the VBA code into C#, which is then deployed in a .dll along with the database.
Now, the VBA code calls into the C# to do the business logic, then the VBA continues to do the displays/UI, while Access still hosts the database.
The problem comes in that I have a report that is being run after the business logic from the C# in one place, and apparently MS Access has a cache, which clears every 5 seconds. So, the transaction that occurs in the C# code writes to the database, but the VBA code is still using the cache. This is causing errors, as the records added to the database (which the VBA report is trying to report on) don't exist in the cache yet...
I'm guessing that the C# .dll must be getting treated as a "second connection" to the MS Access database, which is what seems to typically cause this error in my searches (thinks that one process is writing, and the other is reading).
Since the cache is cleared out every 5 seconds, we can just put the process to sleep, and wake it up after 5 seconds, and then run the report, but that's pretty terrible for an end user.
And, making things difficult, the cache seems like it only gets used in the deployed version (so, when running from source / in debug mode, the error never happens).
Doing some searches, there seems to be plenty of people who have said "just refresh the cache." But, the question is: within VBA, how do you refresh the cache?
Any advice would be welcome.
Thanks
I've been fighting the same issue for years as I write a lot of tools around an old Powerbuilder application that has an Access MDB back end.
The cache does exist and it is VERY real. When data is inserted on a different connection than it is queried on, the cache can be directly observed and measured. It was also documented by Microsoft before they blackholed a bunch of their old articles...
Microsoft Jet has a read-cache that is updated every PageTimeout milliseconds (default is 5000ms = 5 seconds). It also has a lazy-write mechanism that operates on a separate thread to main processing and thus writes changes to disk asynchronously. These two mechanisms help boost performance, but in certain situations that require high concurrency, they may create problems.
I've found a couple workarounds that are not the best, but somewhat make due until I find something better or can re-write the app with a better back end database.
The seemingly best answer I've found (that may actually work for you since you say you need VBA) is to use JRO.RefreshCache. I've been trying to figure out how to implement this using C# or VB.net without any luck. Below is a link to a code example where you execute the RefreshCache method on your 2nd connection that needs to pull the data. I have not tested this myself.
https://documentation.help/MSJRO/jrmthrefreshcachex.htm
A workaround I've found that will deliver the query results within 500ms to 1000ms of insert time (instead of anywhere between 500 and 5000 ms - or more):
Use System.Data.ODBC instead of OleDB, with connection string: Driver={Microsoft Access Driver (*.mdb, *.accdb)};Dbq=;
If someone knows how to use the JRO.RefreshCache method with OLEDB and C# or VB.net, I'd be forever grateful. I believe the issue is it's looking for an ADO connection to be passed in, not an OLEDB connection.
I not aware of ANY suggesting that some 5 second cache exits? Where did this idea come from????
Furthermore, if you have 5 users, then you not going to be able to update their cache, are you?
In other words, the issue of some cache for one user still not going to solve or work with mutli-users anyway, is it?
The simple matter is if you load up a form with 100 reocrds, and then other users are ALSO working on that 100 rows, then all users will not see other changes until such time you tell access to re-load the form.
You can do this with a me.Refresh in the form, and then it will show changes made by other users (or even your c# code!!!).
However, that not really the soluion here.
How does near EVERY system deal with this issue?
Answer:
You don't, you "design" the software to take the user work flow into account.
So, in place of loading up a form with 100 rows of data? (which you should not, unless SUPER DUPER reason exists for doing that).
The you provide a UI in which the user FIRST searches for whatever it is they want to work on.
In other words, say you just booked a user on a tour. Now, they call the office back, and want to change some details of that tour. But, a different tour staff might pick up the phone. So, now a 2nd user opens the tour?
So, you solve that issue by NOT loading all the tours into that form in the first place.
you provide a search screen, so they can search for the user, find the user, maybe type in a invoice number or whatever.
You display the results in a pick list, and then launch the form to the ONE record (and perhaps detail records from child tables).
So there no concpet of a cache in Access anymore then there is in c#.
However, if you load up a datatable in c#, and then display that data?
Well, what about the other users on that system. They will not see changes to that data ANY MORE then the current access form.
So, if you want to update some data in c#? Then fine, but you need/want to do two things:
First, before you call any c# code that may update the current form reocrd? You need to FORCE a data save of that current record BEFORE you call any code, be it VBA code, or c# code that going to update that current reocrd the user is working on.
You can in Access save the current reocrd in MANY different ways, but the typical approach is:
' single record save - current record
if me.dirty then me.dirty = false
' VBA or c# code goes here.
' optional refresh the current form to reflect changes
me.Refresh
So, in most cases, it is the "design" of your software that will solve this issue.
For example, in the tour example, or in fact ANY system, the user can't work, can't update, and can't do their job UNLESS they first find/search and have a means to bring up that form + record data in the first place.
So, ANY typical good design will:
Ask the user for that name, invoce number or whatever.
Display the results of the search, and THEN allow the user to pick the record/data to work on. When they are done, they close that form and are RIGHT BACK to the search form to do battle with the next customer or task or phone call or whatever.
So, a search form might look like this:
In above, I typed in smi, and then displayed a pick list.
The user can further type in say part of the first name, and thus now get this:
So, maybe they type in a invoice number, customer number, booking number or whatever.
So, you display the results, and then they can select the row or "thing" to work on.
thus, we click on the row (or above glasses button), and then jump to the ONE record.
so, the user does whatever they have to do with the customer. Now, when done, they close the ONE thing, the ONE main reocrd.
This not only saves the data (so others in the office can now use that booking data), but it also means the data is saved. and they are NOW right back at the search screen, ready to do battle with the next customer.
So, not only does this mean we have a VERY bandwith friednly design (we only pull the one main reocrd into that form), but it also is better for work flow.
The Access form's cache thus becomes a non issue, since we only dealing with the one record.
And as I pointed out, if the system is multi-user, then you NOT going to be able to udpate and deal with multiple users cached data anyway, are you?
Think of ANY system you EVER used from a software point of view.
When you use google, does it download the WHOLE internet, and then you use ctrl-f to search megs and megs of data in the browser?
Nope!
you search first, get a list of that search, and THEN pick one!!
And when that list is display, maybe others on the internet are udpateing, and add new data - but if that was cached in your browser, then it would not work!!!
And same goes for a desktop accounting system. You don't load up all accounts, and THEN have the user go ctrl-f to search all the data. You search for the customer, invoice number and PICK ONE to work on.
And it does not make sense to load up a form with 1000 customers, and then go ctrl-f to find that customer. Same goes for a instant banking machine. It does not download ALL customers and THEN let you search. It asks you FIRST to get what you need. So, be it browser based, desktop based, or JUST ABOUT ANY software you use?
You quite much elminate the cache issue, since not pre-loading boatloads of data, but asking and letting the user search for the data they need.
So, in regards to the Access form data and cache?
If you are on a form, and call VBA code, or c# code or whatever?
If that code update the current form, you have NO MORE OR LESS of a issue when calling VBA code, or c# code!!!! If that code updates the current form, and the reocrd is dirty (has pending edits), then you get that message about the current form's reocrd having been udpated by another user!!!
So, your cache issue does NOT IN ANY WAY exist MORE or LESS as a issue in typical Access software.
As a genreal rule, if you are on a form with pending edits, and say want to pop up some form to edit releated data?
You have to ensure that pending edits are SAVED before you launch an form that can edit the same data, or run code that can/may edit that data.
As a result, ZERO cache issues should exist, and they no more or no less exist when calling sql or VBA update code in a form then calling some c# code from that form.
So, write the pending update for that form.
Then run your VBA, SQL, or c# code.
And then do a me.Refresh to display any changes made by those external routines.
there is no documetjion, or ANY article I can find that suggests some kind of 5 seocnd cache or update - it is a urban myth, and your software challenge here in regards to use c# or VBA, or even SQL server stored procedures?
They are all the same issue, and I dare say that often access is used as a front end to SQL server, and ALL OF the SAME issues exist when using SQL server with ms-access.
In Youtrack 6.5, is it possible to generate a search query which lists all issues that have been updated since the user have viewed them?
Like -read and #Unresolved (unfortunately this only displays issues that have been read at least one time)
The reason behind this is: It's quite difficult to determine which tasks you need to answer to or take care of. Especially in a team having updates on tasks during the day.
Or is there another way to manage such "unseen changes" in issues (maybe just for those you are watching on)? Or is there something similar to an inbox (except for notifications via eMail)?
No, it's not supported. Have a look at https://youtrack.jetbrains.com/issue/JT-19610
After using youtrack for quite a while my organization is considering a move to JIRA (because of many reasons). However JIRA doesn't seem to include a youtrack importer/migration out of the box (though there seems to be plenty of importers/migrations the other way around).
Has anyone migrated from youtrack to JIRA and have any experience in this?
Edit:
To anyone who might have this problem later, my final solution ended up something like this:
transfer all "basic" data by hand (user accounts, basic project setup etc)
write a small C# program using the atlassian sdk and the youtrack sdk that transfers from one to the other (creating empty placeholder issues if issues was missing due to someone deleting them in youtrack in order to keep numbering).
This approach worked good enough and I managed to transfer pretty much all data without any loss of any very important data (though of course all timestamps are messed up now, but we saw that as an acceptable loss).
Important to know is that youtrack handles issues moved from one project to another a bit counter-intuitive (they still show up in their first project even when they're moved away from there, but they have an issue id from their new project - a slight wtf when I ran into that the first time).
Also, while the atlassian sdk did allow me to "spoof" the creator of an issue (that is, being logged in as used A and creating an issue while telling the system that it's actually user B who is creating this issue) it does not allow you to do this with comments. So in order to transfer those properly I had to actually loop through the comments and log in with the corresponding new user and post the comments.
Also, attachments from youtrack was a bit annoying to download, so I ended up having to download those "by hand". :/
But all in all, it was relatively pain-free. Some assembly required, some final touch-ups required, but it was all done within a couple of days.
I had the same problem. After a discussion with JIM (Jira Importer) developer, I used YouTrack Rest API and Python script to make JSON files. Then I used JIM JSON import.
With this solution you can import almost all fields from YT - the standard one and files with description, links between issues and projects and so on...
I don't know if I can push it to GitHub, I have to ask my boss - I did it during my work hours.... But of course you can ask me if you want.
The easiest approach is probably to export the data from youtrack into CSV and use the JIRA CSV importer. You may have to modify some of the data to fit the expected format for the CSV importer
I have about 40,000 images up on S3 and I've downloaded into my application/database then sent them out to another site (like ebay or magento)
This is to support a client that sells his products on a few sites. Sites which really you'd rather keep a copy of the product image on their site. (so they can resize it and such)
My issue right now is that I want to poke S3 every once and a while looking for new files, or modified files.
I don't much like the idea of targeting each file one at a time. Nor do I like the idea of bringing down all the file names and dates and then comparing them with dates I've stored. Both seem to be quite wasteful especially if I want to run this every day (or every hour).
What I had hoped for, and what I'm looking for is a way to say "give me the names of all the files that have changed since 2013-10-14 13:10:30. This would let me store just one value, and if nothings changed, then I'd get back nothing (or something that indicated nothing).
Is there a way to get a list of changed files since X date?
I'm language agnostic.. though Ruby/Rails would be cool.
Note: I've tried to figure it out with the WSDL, but it doesn't quite seem to help as much as I'd hope.
Unfortunately S3 does not offer any support for this.
Currently your only options are to either list all the objects in the S3 bucket and check for changes or to keep track of the changed objects separate from S3 (record the last changed timestamp in some data store when you change the objects).
I have almost exactly this problem. I say, almost exactly because the answer that worked for this gentleman did nothing whatsoever for me. I can open my own database and see all of the lovely RS data sitting there staring at me but the actual Reporting Services installation still can't. This all came about because of precisely what he said. We accidentally left the password policy on on the Reporting Services account and it expired. When I changed it the whole thing went kaputt. I'm still getting the "key cannot be used in current state" error message even after dropping all encrypted data from the RS installation. I have no access to the Report Manager to reset encrypted information. Has anyone got any suggestions?
EDIT: In continuing my research I found this suggestion. It's not that.
Well... here's the thing.
I eventually tried creating a whole new user to take charge of the SSRS operations. I also remembered to update those details on our live data server. (I did this first and it failed to work as it was still telling me the key could not be used then.)
I guess that there must be something that prevents the reassignment of the SSRS gofer account's password. The new user is set up identically and works perfectly. So that's what cleared it up for me but I'm a little irritated that I still don't know exactly why...