Shulou(Shulou.com)06/02 Report--

This article mainly introduces "how to master the principle and mechanism of ADO.NET resource manager". In daily operation, I believe that many people have doubts about how to master the principle and mechanism of ADO.NET resource manager. The editor consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful for you to answer the doubt of "how to master the principle mechanism of ADO.NET resource manager". Next, please follow the editor to study!

Each resource used in the transaction is managed by the resource manager, whose operations are coordinated by the transaction manager. The coordination between the resource manager and the transaction manager ensures atomicity and isolation for the application. For example, Microsoft SQL Server, persistent message queues, and hash tables in memory are all ADO.NET explorer.

ADO.NET Explorer can manage persistent or mutable data. The persistence of the resource manager (instead of variability) refers to whether the resource manager supports failure recovery. If the resource manager supports failure recovery, it saves the data to the persistent store at stage 1 (preparation phase), so that if the resource manager fails, it can re-enlist in the transaction when restoring and perform the appropriate action based on the notification received from TM. In general, variable resource managers manage variable resources such as in-memory data structures, such as in-memory transactional hash tables, while persistent resource managers manage resources with more persistent backup stores (for example, databases whose backup storage is disk).

For a resource to participate in a transaction, it must enlist in the transaction. The Transaction class defines a set of methods that provide this functionality, and the names of these methods begin with Enlist. Different Enlist methods correspond to different types of enrollment that the resource manager may have. Specifically, the EnlistVolatile method is used to register variable resources, while the EnlistDurable method is used to register persistent resources. For simplicity, after deciding whether to use the EnlistDurable or EnlistVolatile method based on the persistence support of the resource, you should implement the IEnlistmentNotification interface for the resource manager to enroll the resource as participating in a two-phase commit (2PC). For more information about 2PC, see committing transactions in single-phase and multi-phase.

By enlisting, the resource manager ensures that callbacks can be obtained from the transaction manager when the transaction is committed or aborted. Each enrollment has an instance of IEnlistmentNotification. Typically, enlistment is performed only once per transaction, but the resource manager can choose to perform multiple enlistments in the same transaction.

After enlisting, the ADO.NET resource manager responds to the request for the transaction. The persistent resource manager stores enough information to allow transactional work to be undone or redone on the resources it manages. There are many ways to do this; the two most common methods are saving the data version and saving the change log.

When the application commits the transaction, the transaction manager starts the two-phase commit protocol. The transaction manager first asks each enlisted resource manager if it is ready to commit the transaction. The resource manager must be ready to commit, that is, it is ready to commit or abort the transaction.

During the preparation phase, the persistent resource manager records the old and new data to fixed storage so that the resource manager can recover the data even if the system fails. If the resource manager is ready, the transaction manager is notified of a vote on whether it commits or aborts the transaction. If any resource manager reports a failed preparation, the transaction manager sends a rollback command to each resource manager and indicates to the application that the commit failed.

When ready, the resource manager must wait until it obtains a commit or abort callback from the transaction manager in phase 2. Typically, the entire preparation and submission protocol can be completed in less than a second. If a system or communication failure occurs, the submission or suspension notice may not be delivered within minutes or hours. In the meantime, the resource manager will not be able to determine the result of the transaction, that is, it does not know whether the transaction has been committed or aborted. When the resource manager is uncertain about the state of the transaction, it keeps the modified data by keeping the transaction locked, thus isolating these changes from any other transaction.

If the resource manager fails, all enlisted transactions will be aborted except for transactions that were prepared or committed before the failure. When the persistent resource manager restarts, it reconstructs the committed status of the resource by retrieving the preparation information written during the preparation phase, and commits or aborts these transactions accordingly.

In short, the two-phase commit protocol and the resource manager work together to make transactions atomic and persistent.

The Transaction class also provides an EnlistPromotableSinglePhase method to register promotable single-phase enrollment (PSPE). This enables the persistent Resource Manager (RM) to host and "own" transactions that can later be upgraded to be managed by MSDTC when needed.

At this point, the study on "how to master the principle and mechanism of ADO.NET Explorer" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.