From the course: SQL Server Performance for Developers

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Transaction isolation

Transaction isolation - SQL Server Tutorial

From the course: SQL Server Performance for Developers

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Transaction isolation

- [Instructor] Our next topic is isolation levels, and this is a very under-looked part of database performance. The isolation level for your transaction can affect a number of performance components. How locks are taken, how locks are escalated when data is being read, how long those relocks can be held, and whether or not rows updated by another transaction can be read before they're committed. Low isolation levels do allow for more users to be able to access the data so you can get greater concurrency, but they can also affect data integrity by creating the effect of lost updates and dirty reads. Dirty reads are a phenomenon where you read uncommitted data. That data could be wrong, because its transaction hasn't been completed yet. Higher isolation levels, like SERIALIZABLE, can greatly increase blocking, and this can be fairly unpredictable, because blocking is dependent on how many users you have concurrently accessing the system. So if you're application testing does not spawn…

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