If we have ongoing unfinished transactions with any isolation level, does a new transaction with snapshot isolation level wait for their completion before it starts taking a snapshot?
Sorry for My English.
No, it doesn’t. As per Snapshot Isolation in SQL Server doc:
The net effect of snapshot isolation is that the transaction sees all of the data as it existed at the start of the transaction, without honoring or placing any locks on the underlying tables.
also from the same doc:
Snapshot isolation uses an optimistic concurrency model. If a snapshot transaction attempts to commit modifications to data that has changed since the transaction began, the transaction will roll back and an error will be raised.
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