Database Related

What Is The Concurrent Update Problem In Databases?

Multiple sessions of databases are allowed to update the data similar data at one time. This gives rise to concurrent update problem. When the user for database connects to it the session formulated are new, not refreshed. For every user or even the same user, a separate session is lodged. In the complicated boundaries of databases of your application, the event of concurrent update problem is frequent.

Problems

To prevent the concurrent update problem, locking is suggested. If prevention is not taken into consideration, numerous users tend read the database concurrently. Consequently, when transactions access similar data at one time, following problems are home to the databases:

  • Off-track Updates

This is the most common problem which occurs when two or more transactions are carried out at the same time. A transaction is unaware of the other transactions in the same row. Ultimately, the latest update is overwritten by the transactions in the same row. This results in loss of original data.

  • Uncommitted Dependency

This problem occurs when a transaction is taking place and another transaction chooses the same row as the first one, which already is being upgraded. In this way, the second transaction accesses the data which has no liability because of the upgrading session committed by the transaction in the first place.

  • Fluctuating Analysis

The analysis of the second transaction becomes inconsistent when it gains access to read different sets of data every time in the same row.  It is also termed as “non-repeatable read”.  

  • Phantom Reads

When a row in the range of other rows of a transaction is deleted or inserted, that’s when the problem phantom reads occur. Transactions taking place at the same time either insert or delete a row, resulting into a miscommunication of original readings of the rows.

The problems can be prevented by using database locking. It would lock the database, permitting a single user/session of transaction for upgrading. All systems of databases are prone to such breakdowns but there has to be an efficient control over concurrent update problem.

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