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Is there built-in way to access databases in Suave?
Suave is a web server library, so it doesn't come with a built-in way to access a database or anything like a sql abstraction.
An option if you're looking for a framework that does have a way to access data built in, Saturn is a fine choice. It's also used as the backend for SAFE-stack if you're interested in full-stack F#.
Under the covers it's relatively simple, the template just lays down a CLI that lets you scaffold out some code and do migrations. And Dapper gets used as your database access library. But it does at least put things together in a template so that you can see how to connect things.
We have an S/390 mainframe at my new job that’s been running COBOL applications since the late 90’s. The mainframe is getting old enough that we need to migrate to a newer system. We’re a small enough business that we can’t warrant spending the money to upgrade to new mainframe hardware and the program logic has been a constant work in progress for 30+ years, so it has a lot of functional value. I’ve been considering moving the functionality to a Linux machine and using something like OpenCOBOL to recompile as an executable binary instead of trying to rewrite it in a newer language. I haven’t messed with a mainframe enough to have any clue how or where to access this information and the gentleman that wrote all of the programs is unfortunately no longer with us. I’ve read that SSH is an option, but I’m not even sure how to get the ball rolling on that with a mainframe. I use Linux on a fairly regular basis, so I’m familiar with SSH, but from my understanding those mainframes aren’t a simple OS that you can merely connect to and navigate the file system to retrieve data like we can in modern operating systems. Can anyone give me some pointers to get a sense of direction for accessing the source code for the COBOL programs? Are there default locations that they are stored, etc.? They’re somewhat simple programs that don’t use any DB2 functionality and will hopefully compile on a different system with relatively minimal debugging and fixes. I’m certain that I’ve left out necessary information that would help getting an answer to this question, and I can provide any additional information that is needed to help you all help me. I suspect that SSH isn’t enabled by default, but maybe I’m wrong there too. Any assistance is greatly appreciated. Thanks everyone!
Although not a programming question I'll provide some guidance I think might help you.
First, this is a business decision about where to invest.
Do we upgrade the system to a newer model and upgrade some software and acquire the skills to keep the system running? (System Programming, OS upgrade and cost of migration, newer platform (used z13 could be an economical option, storage systems to support the mainframe)
Migration of existing workloads to other platforms. (Cost to migrate code, sizing of performance needs, new technologies to replace existing access methods like VSAM or dare I say ISAM if the applications are old enough)
Status Quo ... leave things where they are and keep the lights on
In evaluating any option you have to assess the risk to the business and what would a disruption cost? IMHO, its less about a technology like SSH or COBOL on Linux but requires some serious assessment of the current state, the acceptable to be scenarios and the cost of pursuing one of those options.
My comments are not intended to instill fear but provide a framework of how do I approach analyzing a challenge of this magnitude.
There is no default location where source code is stored on z/OS (it is z/OS you're talking about, right?). Source code is usually stored in PDS data sets. The naming of those depends on the installation, i.e. the company, and whether or not any software like Endevor, ChangeMan, etc. is being used to maintain the sources.
Since this is old z/OS (OS/390) COBOL code, chances are the code is making use of OS specifics such as record level I/O, VSAM data sets, etc. These are the parts that will not work on a non-z/OS platform without major rewrite. So, you will need to look into the sources.
SSH is available on z/OS, but it needs to be configured and enabled. You need to check with your z/OS sysprog. FTP, and NFS are other options, but again, they need to be configured and enabled.
Transfering the sources is the least of your problems, I'd say.
I have to agree with the prior two answers, but have some additional suggestions. This is a business decision what to do on the system.
Finding the program to understand what it does is the first requirement. Since you know what program is running that may be the name of the source file. That you will need to find. The source file probably will be in some library manager, the first place to look is in the ISPF menu system. There will be an option for the library manager you are using if you are using one. Based on your description you may be using something called SCLM which would should up, or you might see Librarian or Panvalet. You will need to get into ISPF by connecting using a 3270 connection emulator. Once you find the file, using FTP or SFTP may be the best, or your emulator may just provide a transfer mechanism. You will need to find the related files as well, which should also be defined in the library manager.
Once you have the file, you will need to figure out what it uses as mentioned above, it will be working with some kind of data file, and that will be the biggest part to deal with.
If it is a batch program it is probably part of a schedule, and there are other programs also running that you will need to find and figure out how they fit together.
Once you have an understanding of all the parts then you can work to make the right business decision as to how this should be run. You may want to upgrade, you may want to look to getting z/OS as a cloud service if you don't want to upgrade but you want the function. Or it may be a simple program you could move. That will be much easier to figure out once you have the details.
You say the program logic has changing for 30+ years. Was it only one person making all the changes ? Would anyone on the team have some idea about the PDS's that the user had access to ? That might be one of the places to look for. As the previous answers suggested , most shops would have store the source code in some kind of config mgmt tool like SCLM or panvelet. If you have access to the load code, there are utilities that can be used to inspect the load member to get a CSECT listing which would have the names of the obj members that make up that load.You can check with your mainframe admins. That can get you the source code file names. We use SSH from USS in our shop to move code from a HFS folder to gitlab. I have also used plain FTP to just transfer source code files to my workstation . But yes, first you have to find where it is stored.
I'm looking at designing and building out a system that would allow A/B testing of different flows in an iOS app (e.g. registration flow, log-in flow, purchasing flow).
A system that comes to mind initially looks like:
app pings server, server responds giving list of resources (which could include some links to xib files)
if the user does not have those xibs on disk, download them and save them to disk
when the view controller is presented, load from the xib if it has been downloaded (else default to the one the app was shipped with)
Does anyone have any thoughts on this idea or any insights on this system?
NOTE: I am not trying to implement a system where I can add new features. Right now, I'm focusing on changing flows, like the text and views a user will see. I'm not looking into a discussion of whether this violates the App Store rules, but if you would like to do so - go for it!
This is possible, but I don't know if I would download XIBs to the device. Seems a little risky to me.
Apple did a talk at WWDC 2010 where they address this exact issue, and they recommend building the interface using (more or less) Plists or JSON to describe the UI elements and their functions, and building up the views dynamically. It's well worth watching as it brings up a lot of smaller issues that aren't immediately obvious, but it requires a developer account to access it).
This would be an interesting system to use. I wonder if one could write a shell script to replace the old binary of an app with a new one. I know it would probably be more complicated then just that, but it would be cool to do. I would definitely use this for in house apps, or personal tools. Its to bad the apple wouldn't allow it, unless someone could secretly slip it past them :-)
I say go for it. You seem to have a pretty good idea of what you want to do and how you want to do it. Changing the UI based on responses from a server isn't uncommon, but I guess downloading xib files from the server is. I don't see why it wouldn't work though and I don't think it would be rejected by Apple, but you never know.
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Okay, I will shortly be starting down the path of windows mobile development. I know nothing about the subject really and I am looking for people with experience to let me know of any gottchas you may know of.
Right now I dont even have a breif of what is requied but the assumption is that the application will be very little more than a bunch of CRUD forms for updating data. The only other requirment knowladge I have is that the application will need to support offline storage when there is no signal avaliable. This in turn will obviously require some kind of syncronization when signal returns.
My initial thoughts are that the application will primarily be a front end to interact with a web service layer. Im assuming that WCF will be an appropriate technology for building these services? I also thought that SQL Server CE would be a good route to go down with regards to the offline storage issues.
Any knowlage that you feel is useful within this domain would be appreciated. Advice, links, books anything appreciated.
EDIT: It has been noted that there are two ways to go with off-line synchronization. To either use some form of message queuing or to use SQL synchronization tools. Could anyone offer a good comparison and introduction to these?
EDIT 2: After a little more digging I get the impression that there are basically 3 different approaches I can use here:
Emmbeded Database to query against then syncronization online, when able
MSMQ along with .NET remoting
WCF with ExchangeWebServiceMailTransport bindings using Exchange Server.
Now, there has been a nice few points raised on the first issue, and I think I understand at some level the issues I would face. But I'd like to get a little more information regarding MSMQ implementations and using WCFs new bindings.
Here a few words from my experience so far (about 9 months) of .net Windows Mobile development.
Well you are occasionally connected. (Or more likely occasionally disconnected). You have to choose whether you are going to use messaging with queues (i.e. WCF/SOAP/XML or something like it) or database synchronisation. I choose the SQL synchronisation route so I can't really comment on messaging. The SQL synchronisation route is not hassle free!
If you go down the sync route with SQL compact like me you basically have two choices. SQL Server merge replication or the newer ADO.NET Synchronisation services. If you choose the former you need to be really careful with your DB design to ensure it can be easily partitioned between mobile subscribers and the publisher. You really need to think about conflicts, and splitting tables that wouldn't normally be split in a normalised DB design is one way of doing that. You have to consider situations where a device goes offline for some time and the publisher DB (i.e. main DB) and/or a subscriber alters the same data. What happens when the device comes back online? It might mean resolving conflicts even if you have partitioned things well. This is where I got burnt. But SQL Merge Replication can work well and reduces the amount of code you have to write.
Roll your own DAL. Don't attempt to use datareaders etc. directly from UI code and don't use typed datasets either. There may be third party DALs that work with Windows Mobile (i.e. I know LLBLGEN does, might be worth a look) but Linq-to-SQL is not supported and anyway you need something lightweight. The chances are the DAL won't be too big so roll it yourself.
If you are using .net you'll probably end up wanting some unimplemented platform features. I recommend using this inexpensive framework to give you what your missing (especially as related to connectivity and power management) - http://www.opennetcf.com/Products/SmartDeviceFramework/tabid/65/Default.aspx
Windows Mobile devices partially switch off to save power when not in use. If you are doing a polling type design you'll need to wake them up every x mins. A normal .net timer class won't do this. You'll need to use a platform feature which can be used from OpenNetCF (above). The timer class is called LargeIntervalTimer and is in the OpenNetCF.WindowsCE assembly/namespace (I think).
Good Luck!
SqlCE is only one of the options available for local data storage on a Windows Mobile device, and although it's an excellent database it has limitations. For one thing, SqlCE will not work (period) under encryption (in other words, if your user encrypts the location where your SDF file is, you will no longer be able to access the data).
The second (and most critical) weakness of SqlCE lies in the RDA/Merge Replication tools. SqlCE Merge Replication is not 100% reliable in situations where the network connection can drop during replication (obviously very common in Windows Mobile devices). If you enjoy trying to explain missing or corrupted data to your clients, go ahead and use SqlCE and merge replication.
Oracle Lite is a good alternative to SqlCE, although it too doesn't work properly under encryption. If encryption is a potential problem, you need to find a database engine that works under encryption (I don't know of one) or else write your own persistence component using XML or something.
Writing a WM application as a front end that primarily interacts with a web service in real time will only work in an always-connected environment. A better approach is to write your application as a front end that primarily interacts with local data (SqlCE, Oracle Lite, XML or whatever), and then create a separate Synchronization component that handles pushing and pulling data.
Again, SqlCE merge replication does this pushing and pulling beautifully and elegantly - it just doesn't work all the time. If you want a replication mechanism that works reliably, you'll have to write your own. Oracle Lite has something called a snapshot table that works very well for this purpose. A snapshot table in Olite tracks changes (like adds, updates and deletes) and allows you to query the changes separately and update the central database (through a web service) to match.
This thread I just posted on SO a few days ago has proven to be a great resource for me thus far.
Also the Windows Mobile MSDN WebCasts are a wealth of information on everything from just getting started up to advanced development.
I would suggest Sqlite for local storage. From the last benchmark I ran it was much better than SqlCe and you don't have to do stupid things like retain an open connection for performance improvements.
Trade-offs being that the toolset is less rich and the integration with other MSSql products is nil. :(
you might want to refer to this:
getting-started-with-windows-mobile-development
You shouldn't be intimidated for windows mobile development. It isn't much different from desktop development. I strongly recommend that you use .NET Compact Framework for development and not C++/MFC.
Some useful links:
Mobile section at the Code
Project. You would find a lot of
articles, a little digging is needed
to find the appropriate one.
Smart
Device Framework from OpenNetCF
offer valuable extensions to the
compact framework.
When you install
the Mobile SDK, you will find under the
Community folder links for the
Windows Mobile and CF framework
blogs. These are also valuable
resources.
Regarding your application, you are right about the WCF and the SQL Server CE. These are the proper ways for handling communication and storage.
Some hints for people coming from a desktop world:
You need to have some sort of power management. The device may automatically go to suspend state. Also, you shouldn't consume power when you don't have to.
Network connectivity is a difficult issue. You can register notifications for when a specific network (Wi-Fi, GPRS) becomes available or unavailable. You can also set the preferred means of communication.
Make the UI as simple as possible. The user uses his thumb and/or a pen and he is probably on the move.
Test in a real device as early as possible.
"24 Hours of Windows Mobile Application Development" from the Windows Mobile Team Blog has some good resources
If you can, try to start from the user use cases and work back to the code, rather than vice versa. It's really easy to spend a lot more time working on the tools than working on the business problem. And thinking through user requirements will help you consider alternate strategies, because a lot of the patterns you know from normal .NET don't apply.
I've done lots of intermittent application development of exactly the type you are describing, and an on-board database works just fine. The MSMQ/WCF stuff just adds conceptual overhead without adding much value. You need a logical datastore locally anyway, and replication at this level is a simple concept that you want to keep simple, so the audit trail is easily monitored and debugged. MSMQ and WCF tend to hide things in unfamiliar places.
I upvoted the SqlLite suggestion BTW. MS doesn't have their persistence story stabilized yet for CE.
For the database replication bit I highly recommend Sybase Ultralite. In terms of flexibility and performance it knocks the socks off SQL CE
I had to do this once. Weird setup with Macs for development, and we were all Java programmers. And a short deadline. PowerPC macs too, so no chance to install Windows for Visual Studio development, never mind that the money for this would never have appeared.
We ended up writing applications using Java, running on the IBM J9 virtual machine, with SWT for a user interface. Entirely free development stack. Easy to deploy. Code ran on any platform we desired, not just PocketPC/WinMob.
Most of the work was on the server side anyway - the database, the web service server. The logic. The reporting engine. The client side wasn't totally simple however - would get the form templates from the server (because they changed frequently), the site details (multi-site deployment), generate a UI from the form template (using some SWT GUI components that are wonderful for PocketPC development, like the ExpandBar), gather data with a point and click interface (minimising keyboard entry where possible), and then submit it back to the server.
For offline storage we used XML files on the device itself. More than enough for our needs, but yours may differ. Maybe consider SQLite?
There are a couple links you can check out to start with:
http://developer.windowsmobile.com
http://msdn.microsoft.com/en-us/windowsmobile/default.aspx
If you have a sticking point while developing, there are also Windows Mobile dedicated chats on MSDN that you can attend and ask your questions. The calendar hasn't been updated yet, but the next ones should be in January. You can find the schedule here: http://msdn.microsoft.com/en-us/chats/default.aspx
I am going to add an additional question to this post, as its been active enough and hopefully will be helpful to others as well as me. Ok, so after playing around I now realize that standard class libraries cannot be included in windows mobile applications.
Now the overwhelming advice here seems to be use an embedded database, though I now do have use cases and it appears that I will need to have document synchronization as well as relational data. With this in mind service layer interaction seems inevitable. So my question is how would I share common domain objects and interfaces between the layers?
"Document synchronization" - does that mean bidirectional? Or cumulative write-only? I can think of mobile architectures that would mainly collect and submit transactions for a shared document - if that's your requirement, then we should discuss offline - it's a long (and interesting) conversation.
Owen you can share code from Compact Framework -> Desktop, it's only Desktop -> Compact Framework that has compatability issues if you use certain objects that are not supported by the CF.
While a desktop lib doesn't work on CF a CF lib WILL work on the desktop, you can also run CF.exes on the desktop!
Just create a CF library as the project that defines your base objects / interfaces etc.
This book sshould e essential reading for all Windows Mobile developers: http://www.microsoft.com/learning/en/us/books/10294.aspx
For developing windows mobile applications you must have the basic tools like silverlight, visual studio, windows phone emulator and sqlite as your database storage.
I am developing a cocoa application that will be making heavy use of both web services and a standard dbms (most likely MySQL) and I am wondering if anyone has a good option for a database library or ORM solution they have used. CoreData is not an option due to the need to support a standard DBMS and to be able to modify the data outside of the normal application operation.
I have found a number of possible options from new open source libraries:
http://github.com/aptiva/activerecord/tree/master
To writing my own wrapper for the C MySQL api.
Any advice is welcome,
Thanks!
Paul
We faced a similar question when we first started work on Checkout, our solution was to code the entire app in Python, using PyObjC. Checkout 1 had an sqlite backend, Checkout 2 has a postgres backend.
There are a couple of really mature and powerful ORMs on the Pyton side, such as SQLObject, which is pretty simple to work with (we used it for Checkout 1.0) and SQLAlchemy, which is more powerful but a bit harder to wrap your brain around (we used it for Checkout 2.0).
One approach you could evaluate, is building the application in Objective-C, but writing the data model and database connectivity/adminstration code in Python. You can use PyObjC to create a plugin bundle from this code, that you then load into your app That's more or less the approach we took for Checkout Server, which uses a Foundation command-line tool to administer a postgres server and the databases in it, this CLI tool in turn loads in a Python plugin bundle that has all of the actual database code in it. End-users mostly interact with the database through a System Preferences pane, that has no clue what the database looks like, but instead uses the command-line tool to interact with it.
Loading a plugin is simple:
NSBundle *pluginBundle = [NSBundle bundleWithPath:pluginPath];
[pluginBundle load];
You will probably need to create .h files for the classes in your bundle that you want to have access to from your Obj-C code.
You might also want to check out the BaseTen framework. It is a Core Data-like framework (in fact, it can import Core Data models), but works with PostgreSQL (though not MySQL, as far as I know). It includes some very nice features such as schema discovery at run time. It also includes an NSArrayController subclass that automatically handles locking and synchronizing across multiple users, so you can continue to make use of Apples Key-value Binding in your UI.
I have personal experience with this particular problem. I even started down the road of writing my own wrapper for the C MySQL API.
The eventual conclusion was: Don't!
The solution that worked in my case was to communicate with the MySQL server via PHP. If you are familiar with web services, chances are that you know about PHP, so I don't won't go into loads of detail about that.
To read from the database:
The cocoa app sends a request for a URL on the server: http://theserver.com/app/get_values.php
The get_values.php script handles the database query, and returns the data in xml format
The cocoa app loads and parses the xml
To write to the database:
The cocoa app sends a more complex request to the server: http://theserver.com/app/put_values.php?name="john doe"&age=21&address=...
The put_values.php script parses the input and writes to the database
The beauty of this solution is that PHP is great for working with MySQL, and cocoa has some handy built-in classes for working with XML data.
edit: one more thing:
One of the key things you have to figure out with this approach is how much processing should be done on the server, and how much should be done in the app itself. Let cocoa do the things that cocoa is good at, and let PHP and MySQL do the things that they are good at.
You could write a generic PHP script to handle all queries: perform_query.php?querystring="SELECT * FROM .....", but that is hardly an optimal solution. Your best bet is several smaller PHP scripts that handle individual datasets for you. In my case, there was one to get the list of users, one to get the list of transactions, etc. Again, it all depends on what your app is going to do.
GDL2 is a nice example, based on EOF.
Instead of reinventing the wheel by writing your own communication wrapper to deal with MySQL from Cocoa, you could try the SMySQL framework (a.k.a. MCPKit), it was part of the CocoaMySQL application that evolved into the Sequel Pro project. It works with varying versions of MySQL, and seems to be quite robust.
If you need to understand how to incorporate it into your application, there's not much documentation around, but it has an easy to understand interface and you can see it working by looking at the source of Sequel Pro, which is downloadable from Google code.
There is also the CocoaMySQL-SBG fork of the CocoaMySQL project, but that seems to be out of date and I couldn't get it to build properly.
I've also implemented a simple object persistence framework based on sqlite, but it certainly wasn't trivial to do. I agree with eJames' conclusion- don't implement one yourself if you don't have to.
If you aren't committed to programming in Objective-C you might want to take a look at PyObjC which would allow you to program the database portion in Python. You can use the MySQLdb module for DB access and there are plenty of tutorials online for its use. It isn't hard to stuff the data back into Cocoa/CF classes and pass them back to your app.
The main caveat with PyObjC is that at the moment it doesn't work with Tiger.