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Hello,

We've (Markus Birkner, Christian_Fels) started two days ago with myWMS and first we would like to thank Olaf Krause for his very good help with the first tutorial.
But we have some questions - maybe someone can help us:
  • Is there a feature-list about myWMS ? We are very interested to see whats already programmed in the system (like FIFO, order chains, ..) ?
  • Is there a javadoc (my eclipse would love it ;-) ?
  • Is there a error-message-guide with error-descriptions ? The one-word-error-messages are good, but as a beginner we would like to have a longer description of possible reasons of errors and possible solutions.

We've done a lot of sql the last few years and see the OO-RAM-database-concept with great interest.
Doing the tutorial made us think about the transaction-concept and what to say - we have some questions:
  • Whats happening if you start a transaction in a client-programm and the programm finishes without doing a commit or rollback ?
  • Is it possible to have several open transactions at the same time ?
  • Is it possible to see open transactions or locked objects "from the outside" ?
  • Is it possible to kill processes / locks from the outside ?

Markus Birkner
Christian_Fels

Is there a feature-list about myWMS?

All I now about is the software documentation and the resources at the community pages. Expecially the documentation and newsletter section. Further information may cummulate here, in the Wiki. --Olaf Krause

Is there a javadoc (my eclipse would love it ;-) ?

Currently the javadoc is published as a result of the Together documentation at http://community.mywms.de/architecture/release-2-0/. I think, we can easily provide a downloadable file with the documentation contents at the download section. --Olaf Krause

Is it possible to have several open transactions at the same time?

Yes. At begin of the transaction a transaction id (tid) is delivered. It will be valid until a rollback, a commit or a TransactionException. One can use as much transaction as one can handle. Additionally the KernelInterfaces are thread safe. --Olaf Krause

Is it possible to see open transactions or locked objects "from the outside"?

Not currently on request. The implementation of the myWMS transactions do provide statistics on transactions. The myWMS cache does provide cache statistics. This is not usable for online debugging, but gives some ideas about what happens to the system. Other implementations of the persistence layer may provide individual features. --Olaf Krause

Is it possible to kill processes/locks from the outside?

If a BusinessObject is retrieved by the getXxxLocked(koi,tid) method, the object is bound to the specified transction. The lock is permament, as long as the transaction lasts (except a call to cancelXxx(bo,tid)). A conflicting call to getXxxLocked(koi,tid) will be blocked, until the previous transaction keeps the objects.

But there is an exception. myWMS' implementation of the persistence layer only blocks for a maximum of 5 seconds in case of conflicting access. After this timeout the blocking transaction is assumed to be malicious and the last version of the object changes exclusivly to the new transaction. Committing the previous transaction will fail in this case.
However, if no conflicting getXxxLocked(koi,tid) to an object happens, the transaction will last infinitly. --Olaf Krause



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