![]() ![]() Re-login to you installation to enable NVM CLIĪfter this you should have node version 9 installed in this path: Create bash profile file (this is required by nvm)Ĥ. You need version 9 of nodejs in your system, easiest way in my opinion to install custom version of nodejs and to not affect version 12 that is present in HiFIBerryOS, is to use nvmĢ. When you execute Transaction 1 and 2 from 2 different instances of SQL Server management studio, Transaction 2 is blocked until Transaction 1 completes, and at the end of Transaction 1, both the reads get the same value for the Quantity of the same product mobile.My build worked for me and my setup which includes: Raspberry Pi 3b, HiFiBerry DAC+ Standart, wired connection (for some reason connection to plexamp drops on wireless), HiFiBerryOS installed With the above changes in place, now run transaction 1 first and then the second transaction and you will see that it gives the same result for both the read in transaction 1. UPDATE Products SET Quantity = 5 WHERE Id = 1001 Modify the Transaction 2 code as follows: - Transaction 2 SET TRANSACTION ISOLATION LEVEL REPEATABLE READ Modify the Transaction 1 code as follows: - Transaction 1 Let us rewrite both the transactions using the Repeatable Read Transaction Isolation Level. This solves the non-repeatable read concurrency issue. This will ensure that the data that Transaction 1 has read will be prevented from being updated or deleted elsewhere. So, let us set the transaction isolation level of both Transactions to repeatable read (you can also use any higher transaction isolation level). In order to solve the Non-Repeatable Read Problem in SQL Server, we need to use either Repeatable Read Transaction Isolation Level or any other higher isolation level such as Snapshot or Serializable. UPDATE Products SET Quantity = 5 WHERE Id = 1001 How to Solve the Non-Repeatable Read Concurrency Problem in SQL Server? SELECT Quantity FROM Products WHERE Id = 1001ĬOMMIT TRANSACTION Transaction 2 - Transaction 2 SET TRANSACTION ISOLATION LEVEL READ COMMITTED I am using READ COMMITTED Transaction Isolation Level in the below transactions to introduce the Non-Repeatable Read Concurrency Problem. So, here, we need to set the Transaction Isolation Level either READ COMMITTED and READ UNCOMMITTED. As we already discussed READ COMMITTED and READ UNCOMMITTED Transaction Isolation Level produces the Non-Repeatable Read Concurrency Problem. Notice that when Transaction 1 is completed, it gets a different value for reading 1 and reading 2, resulting in a non-repeatable read concurrency problem. From the first instance execute the Transaction 1 code and from the second instance, execute the Transaction 2 code. Open 2 instances of SQL Server Management Studio. Non-Repeatable Read Concurrency Problem Example in SQL Server: Transaction 1 then makes a second read for the same product Mobile and it gets a value of 5, resulting in a non-repeatable read concurrency problem. At this point, Transaction 2 starts and it updates the Quantity to 5 for the same product Mobile. Once it reads the data, then it is going to do some other work. Transaction 1 starts first and it reads the Quantity available as 10 for the product Mobile. ![]() As shown in the below image, we have two transactions (Transaction 1 and Transaction 2). ![]() Please have a look at the following diagram which shows the Non-Repeatable Read Problem in SQL Server. INSERT INTO Products values (1003, 'Laptop', 30) INSERT INTO Products values (1002, 'Tablet', 20) INSERT INTO Products values (1001, 'Mobile', 10) Please use the below SQL Script to create and populate the Products table with the required sample data. We are going to use the following Products table to understand this concept. Let’s understand the Non-Repeatable Read Concurrency Problem in SQL Server with an example. Understanding Non-Repeatable Read Concurrency Problem in SQL Server The Non-Repeatable Read Concurrency Problem happens in SQL Server when one transaction reads the same data twice while another transaction updates that data in between the first and second read of the first transaction. What is a Non-Repeatable Read Concurrency Problem in SQL Server?
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