data-konzept

'In this article, I’ll explore the use of snapshot isolation using row versioning as an alternative to the classic ANSI SQL transaction levels.

Modern database systems excel at using the system resources available to them. Those include the CPU, RAM, Network and persistent storage of some sort. Busy systems can have thousands of active sessions, yet each session has the illusion of exclusive access. This is called concurrency and it is fundamental to the operation of most computing systems — even your smartphone!

In relational database systems, transactional isolation – an ANSI SQL standard – is often used to try to maximize concurrency while maintaining the ACID principle. Sometimes that is called pessimistic concurrency, since it assumes that something may go wrong and tries to prevent that from happening. Some database vendors have developed alternative approaches to managing concurrency and SQL Server is no exception. This article looks at snapshot isolation using row versioning as an example of just such an approach. Row versioning can be called optimistic concurrency since it assumes that things will usually go right.'...

https://www.sqlshack.com/snapshot-isolation-in-sql-server/