2. Vector Concepts : Transaction Isolation Model : Transactions and DDL Operations
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Transactions and DDL Operations
Snapshot isolation and optimistic concurrency control are applied to operations on data (DML).
For operations that change the database schema (DDL), a different isolation model is used. In this model, transactions only see DDL changes performed by other transactions after they committed. Still, if there are conflicting DDL operations (for example, two transactions creating a table with the same name), the system locks the second transaction until the first transaction either commits or aborts.