Specifies the transaction isolation level for transactions.
Syntax:
type TTransIsolation = (tiDirtyRead,
tiReadCommitted,
tiRepeatableRead);
property TransIsolation: TTransIsolation;
Description:
Use TransIsolation to specify the transaction isolation level for database transactions. Transaction isolation level determines how a transaction interacts with other simultaneous transactions when they work with the same tables, and how much a transaction sees of the work performed by other transactions.
TransIsolation can be any one of the three values summarized in the following table:
Isolation level |
Meaning |
tiDirtyRead |
Permits reading of uncommitted changes made to the database by other simultaneous transactions. Uncommitted changes are not permanent, and might be rolled back (undone) at any time. At this level a transaction is least isolated from the effects of other transactions. |
tiReadCommitted |
Permits reading of committed (permanent) changes made to the database by other simultaneous transactions. This is the default TransIsolation property value. |
tiRepeatableRead |
Permits a single, one-time reading of the database. The transaction cannot see any subsequent changes made by other simultaneous transactions. This isolation level guarantees that once a transaction reads a record, its view of that record does not change unless it makes a modification to the record itself. At this level, a transaction is most isolated from other transactions. |
Applications that use passthrough SQL for handling transactions must pass a transaction isolation level directly to the database server using the appropriate SQL statement.