What is a possible consistency?

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eventual consistency is a programming model in which programmers assume that for a long time and without changes in the system, the current version of a particular program will eventually distribute until each replica of the program is consistent. The concept of possible consistency is used in programming methods such as optimistic replication, distributed shared memory and distributed transactions. As far as databases are concerned, any consistency is achieved through a three -stage process. First, distributed information is available in the system; This is followed by a soft condition in which different users can still work with different data versions; Finally, consistency is achieved and all computers have access to identical data. For the first few seconds after the update is released, no one will have it; Not enough, I handed over to the users of the software to download and install an update. This is the state of 'available'; The update exists, but must still be distributed. Over time when users downloadThe update, some will have it and some will not. After a lot of time, however, anyone who uses software will be updated to the latest version. This is the prerequisite for the state of any consistency: given sufficient time, each update is fully promoted throughout the system.

Since the system is working on eventual consistency, conflicts are inevitable. This happens when the version of the program or information currently does not match the "model version" of the program. Programs are usually set to recognize and manage these conflicts. If the files on a particular computer are older than the latest versions of the software or data, the system usually begins the user's update to resolve the disparity.

There are three possible methods for performing the following resolution: repair of writing, repair of reading and asynchronous repairs. All these methods bring verZI program or data in accordance with a consistent model. The key difference between them has to do with the system to be repaired. All these operations have advantages and disadvantages.

When repairing the writing, a change in the code stored on the computer is made during writing operation when the computer is already writing something on the hard disk of the system. This fixes inconsistency, brings the program or data in accordance with the model, but also temporarily slows the original registration operation. Reading repair is remedial during the hard disk reading cycle. This in turn slows down reading surgery. Asynchronous corrections are repaired when neither read or write operation occurs, leading to cosp into the CPU.