Question: How Do You Handle Multiple Users Changing The Same Data?

When 2 request comes to the database at the exact same time how will it handle it?

2 Answers.

Even if two cpu’s are handling requests at exactly the same time, and they conflict, then at some stage they will say “I want to do something, which can’t be done at the same time as anything else is happening”..

How do databases handle concurrency?

Whoops! Databases use MVCC to permit concurrent access to the data by giving users the illusion they’re the only ones touching the database. It’s as if they have exclusive access, even though they really don’t. Behind the scenes, the illusion is handled through locking, keeping old row versions, and other mechanisms.

How do you handle concurrent transactions?

You can use Hibernate optimistic locking. Optimistic locking assumes that multiple transactions can complete without affecting each other, and that therefore transactions can proceed without locking the data resources that they affect.

How do I make multiple requests at the same time?

Just create a runner with some requests and click the “Run” button multiple times to bring up multiple instances. I’ve just ran 1500 url’s at once, did lag google a bit but it works. For a simpler GUI approach, open every request you want to run in different tabs . Then you can go to each tab a click run.

How does select for update work?

The SELECT FOR UPDATE statement is used to order transactions by controlling concurrent access to one or more rows of a table. It works by locking the rows returned by a selection query, such that other transactions trying to access those rows are forced to wait for the transaction that locked the rows to finish.

What does limit 1 mean in SQL?

Description. The SQL SELECT LIMIT statement is used to retrieve records from one or more tables in a database and limit the number of records returned based on a limit value. TIP: SELECT LIMIT is not supported in all SQL databases.

How do Web applications handle concurrency?

How do I deal with concurrent changes in a web application?user sends request.server reads data.server modifies data.server saves modified data.

How do Web applications handle multiple users?

User has registered and logged in to the site – so you need a table in your database to contain a list of users – and it would probably help if you had some unique ID in it to identify each user. You can then use ASP.NET session to keep track of which user is active in each session / whether logged in etc.

How multiple users handle same data change in SQL Server?

when a user starts editing, you do this:lock the row (or the whole table if you can’t lock the row)check the flag on the row you want to edit.if the flag is true then. inform the user that they cannot edit that row at the moment.else. … release the lock.when saving the record, set the flag back to false.

What happens when multiple processes threads are trying to modify the same data?

When both threads run EXACTLY AT THE SAME TIME, both threads will be in critical section simultaneously. The only solution (should be in hardware level) would be making each processors run slightly off to each other, but it defeats the purpose of parallelism.

How do you handle multiple users changing the same data in Java?

If the version had been changed, then someone else must have edited the record in the meantime. Your application has to decide how the conflict should be handled. One way is to ask the user to re-apply their changes to the latest data, another might be to show both records and allow user to pick one to save.

What is concurrency in Web applications?

Concurrency, in the context of a software application, is the handling of multiple users attempting to access the same data at the same time. … Once changes are made, the data is sent back to the server, and the database record for that order is updated.

How do you solve concurrency issues in Java?

Immutability. The simplest way to avoid problems with concurrency is to share only immutable data between threads. Immutable data is data which cannot changed. An immutable class may have some mutable data which is uses to manages its state but from the outside this class nor any attribute of this class can get changed …

What is limit clause SQL?

The LIMIT clause is used to set an upper limit on the number of tuples returned by SQL. It is important to note that this clause is not supported by all SQL versions. The LIMIT clause can also be specified using the SQL 2008 OFFSET/FETCH FIRST clauses. The limit/offset expressions must be a non-negative integer.

What happens if two users try to update a database at the same time?

The second person makes some changes and submit them. The row is locked, changed and unlocked. Because the UPDATE and COMMIT operations happen (almost assuredly) in a fraction of a second, the updates performed by the two users may well happen less than a second from each other.

How do you handle concurrency?

The general approach to handle a concurrency conflicts is:Catch DbUpdateConcurrencyException during SaveChanges .Use DbUpdateConcurrencyException. … Refresh the original values of the concurrency token to reflect the current values in the database.Retry the process until no conflicts occur.