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.
I need to extract some data from my client's SAP ECC (the SUIM -> Users by Complex Selection Criteria -program RSUSR002)
Normally I give them a table of values that I they have to fill some field to extract what I need.
They have to make 63 different extractions (with different values of objects, for example - but inside the same transaction - you can see in the print) from their SAP, to later send to me all extracted files.
Do you know if there is an automated way to extract that, so they don't have to make 63 extractions?
My biggest problem is that every time they make mistakes. It's a lot of things to fill..
Can I create a variant and send it to them? Is it possible to export my variant so they can import it without the need to fill 63x different data?
Thank you.
When this is a task which takes considerable effort by multiple people each year, then it is something which might be worth automatizing.
First you need to find out where that transaction gets its data from. If you spend some time analyzing and debugging the program behind the transaction, you will surely find which SELECT's on which database table(s) provide that data. If you are lucky, there might even be a function module for it.
Then you just need to write an own ABAP program which performs the same selections.
Now about the interesting part: How to get that data to you. There are several approaches here. The best one depends on your requirements and your technical infrastructure. Some possibilities are:
Let users run the program in foreground, use the method cl_gui_frontend_services=>gui_download to save the data to a file on the user's PC and ask them to send it to you via email
Run the program in background and save the file on the application server. Then ask your sysadmins how to get that file from their application server to you. The simplest way would be to just map a network fileserver so they all write to the same place, but there might be some organizational hurdles in the way which prevent that. (Our security people would call me crazy if I proposed to allow access to SMB shares from outside of our network, but your mileage may vary)
Have the program send the data to you directly via email. You can send emails from an SAP system using the function module SO_NEW_DOCUMENT_ATT_SEND_API1. This of course requires that the system was configured to be able to send emails (which you can do with transaction code SCOT). Again, security considerations apply. When it's PII or other confidential data, then you should not send it in an unencrypted email.
Use an RFC call to send the data to your own SAP system which aggregates the data
Use a webservice call to send the data to your own non-SAP system which aggregates the data
You can create a recording in transaction SM35.
There you fill a tcode (SUIM), start recording, make some input in transaction SUIM and then press 'Execute'. Then you can go back to recording (F3 multiple times) and the system will generate some table with commands (structure is BDCDATA). You can delete unnecessary part (i.e. BACK button click) and save it to use as a 'macro'. Then you can replay this recording and it will do exactly what you did.
Also it's possible to export/import the recording to text file, so you can explore it's structure, write some VBA script to create such recording from your parameters and sent it to users. But keep in mind that blanks are meaningful.
It's a standard tools so there's no any coding in the system.
You can save the selection as a variant.
Fill in the selection criteria and press Save.
It can be reused.
You can also transport Variants if the they have a special name
I need to log the last time the user signed in using my node.js server. I am looking into three options. The persistence requirement is not super high, meaning that the margin of error of this record being recorded is open.
Use SQL DB and whenever the user logs in it modifies their profile account.
Record it in a server text file. So whenever the user logs on, this file will be opened and updated. The opening, recording and closing of the file will all be done asynchronously.
I'm thinking that the second option is the better on because I'm using SQL for many other operations so I prefer to not interrupting my DB as much as possible.
One concern I have for the second option is the performance hit on the server that will be caused by the frequently read and write to a local text file.
I'm curious what other people who have gone through this path thought about my thought process. Any opinions or tips are highly welcomed. Thank you.
Normally you should use a SQL database, it is a much more better way than the plain text.
The main problem with a text file is that when you log in, you can simply append a line (but what about a couple of user loggin in at the same moment ? You have not any warranty that all the access are logged), but when you want to extact the last login for a user, you should read (and then load) all the file from the start (or the end), which can cause a really worst problem than the access to the DB.
Naturally you can work out all the problems with a text file, but then you have written a lot of code to avoid a simple update query.
I don't think that, with the information you give, you should be worried about the performance of a database access in this case.
Actually I am in need of counting the visitors count for a particular document.
I can do it by adding a field, and increasing its value.
But the problem is following.,
I have 10 replication copies in different location. It is being replicated by scheduled manner. So replication conflict is happening because of document count is editing the same document in different location.
I would use an external solution for this. Just search for "visitor count" in your favorite search engine and choose a third party tool. You can then display the count on the page if that is important.
If you need to store the value in the database for some reason, perhaps you could store it as a new doc type that gets added each time (and cleaned up later) to avoid the replication issues.
Otherwise if storing it isn't required consider Google Analytics too.
Also I faced this problem. I can not say that it has a easy solution. Document locking is the only solution that i had found. But the visitor's count is not possible.
It is possible, but not by updating the document. Instead have an AJAX call to an agent or form with parameters on the URL identifying the document being read. This call writes a document into a tracking DB with one or two views and then determines from those views how many reads you have had. The number of reads is the return value of the AJAX form.
This can be written in LS, Java or #Formulas. I would try to do it 100% in #Formulas to make it as efficient as possible.
You can also add logic to exclude reads from the same user or same source IP address.
The tracking database then replicates using the same schedule as the other database.
Daily or Hourly agents can run to create summary documents and delete the detail documents so that you do not exceed the limits for #DBLookup.
If you do not need very nearly real time counts (and that is the best you can get with replicated system like this) you could use the web logs that domino generates by finding the reads in the logs and building the counts in a document per server.
/Newbs
Back in the 90s, we had a client that needed to know that each person had read a document without them clicking to sign or anything.
The initial solution was to add each name to a text field on a separate tracking document. This ran into problems when it got over 32k real fast. Then, one of my colleagues realized you could just have it create a document for each user to record that they'd read it.
Heck, you could have one database used to track all reads for all users of all documents, since one user can only open one document at a time -- each time they open a new document, either add that value to a field or create a field named after the document they've read on their own "reader tracker" document.
Or you could make that a mail-in database, so no worries about replication. Each time they open a document for which you want to track reads, it create a tiny document that has only their name and what document they read which gets mailed into the "read counter database". If you don't care who read it, you have an agent that runs on a schedule that updates the count and deletes the mailed-in documents.
There really are a lot of ways to skin this cat.
I need a simple tool to visualize the status of a series of processes (ETL processes, but that shouldn't matter). This process monitor need to be customizable with color coding for different status codes. The plan is to place the monitor on a big screen in the office making any faults instantly visible to everyone.
Today I can check the status of these processes by running an sql statement against the underlying tables in our oracle database. The output of these queries are the abovementioned status codes for each process. I'm imagining using these sql statements, run periodically (say, every minute or so), as an input to this monitor.
I've considered writing a simple web interface for doing this, but I'm thinking something like this should exist out there already. Anyone have any suggestions?
If just displaying on one workstation another option is SQL Developer Custom Reports. You would still have to fire up SQL Developer and start the report, but the custom reports have a setting so they can be refreshed at a specified interval (5-120 seconds). Depending on the 'richness' of the output you want you can either:
Create a simple Table report (style = Table)
Paste in one of the queries you already use as a starting point.
Create a PL/SQL Block that outputs HTML via DBMS_OUTPUT.PUT_LINE statements (Style = plsql-dbms_output)
Get creative as you like with formatting, colors, etc using HTML tags in the output. I have used this to create bar graphs to show progress of v$Long_Operations. A full description and screen shots are available here Creating a User Defined HTML Report
in SQL Developer.
If you just want to get some output moving you can forego SQL Developer, schedule a process to use your PL/SQL block to write HTML output to a file, and use a browser to display your generated output on your big screen. Alternately make the file available via a web server so others in your office can bring it up. Periodically regnerate the file and make sure to add a refresh meta tag to the page so browsers will periodically reload.
Oracle Application Express is probably the best tool for this.
I would say roll your own dashboard. Depends on your skillset, but I'd do a basic web app in Java (spring or some mvc framework, I'm not a web developer but I know enough to create a basic functional dashboard). Since you already know the SQL needed, it shouldn't be difficult to put together and you can modify as needed in future. Just keep it simple I would say (don't need a middleware or single sign-on or fancy views/charts).