We have a proprietary accounting application that allows the client to run over the network. It opens the program from the server (running w2k) on the local PC. File locking seems to be handled by w2k share, and the program itself. We tried to run directly from our Buffalo Terastation, and the program seems to run, even with multiple individuals opening the program, and looking at same data base. We are not sure why it works, and are wondering if it would be safe to use, instead of our w2k machine, or a windows 2003 server, since it is very fast. Our problem is we don't know if the Terastation handles the locks, or if the windows PC opening the files is handling the locks. Can anyone help? Our application is a topspeed data base created in Clarion
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We will take your advice and do some testing. I believe we will create some test programs to open multiple files at the same time, and write at the same time to the same records to see if supported.
We had several people search and view same file, and same record, but unable to tell about writing, because program protects against opening record for write by more than one person at a time.
Great suggestions .. thank you !
Michael
Sorry I had not gotten back to you .. We are still working on creating accurate tests to look at all possible combinations of opens, writes, etc. The application is very large with many files, and many records, and written in Clarion code not their app generator. As a result we may need to add some additional locks at the app level just to play it safe. Thank you for your help .. and thank you for the information. Have a GREAT weekend . .. Michael
Just found this ? today, so sorry for the late response. As a long time Clarion programmer I can tell what Clarion does in a multi-user setting.
At the RECORD level. The same record can be accessed by x number of users as a READ. The software will make a second copy of the record in the workstations memory. If changes are made by the user and a save is attempted, the software will reread the record from the database and compare it to the saved COPY in memory. If the 2 are the SAME it will write the changed record back to the database. If the 2 are different the user will get an error message that the "Record had been changed by another workstation" and must edit the record again.
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by: pcelbaPosted on 2009-07-28 at 13:41:43ID: 24965001
Windows PC is opening the file BUT the logic behind it must call the File system on the NAS to fullfil this request. Same procedure is valid for file locking. The NAS must provide interface compatible for Windows file sharing. If the NAS provides just FTP access you can open and read/write the whole file but you cannot lock single records.
All locks must be handled by the file system where open files are stored. The file system only knows who is accessing the file and it is independent on fact if it is W2K folder or shared drive on the NAS. Local Windows PCs are just passing lock requests and waiting for File system responses (it is done through local OS, of course). Windows client PCs don't know about each other so they cannot handle locks on files shared by anybody else.
The Clarion database has its own set of lock commands which is again implemented through OS kernel calls. You can simply test how locks are handled by attempting to edit one data records from two or more PCs. Depending on application design you may observe following behaviour:
1) All instances will allow record editing, the last save is the winner.
2) All instances will allow record editing, the record change by another user is tested before saving.
3) Only one instance will allow record editing, all others must wait.