TransactionType Property

Version: Available or changed with runtime version 1.0.

Sets the transaction type.

Applies to

• Xml Port
• Report

Property Value

Value	Available or changed with	Description
UpdateNoLocks	runtime version 1.0	All read operations are performed with READ UNCOMMITTED locking until the table is either modified by a write operation or locked with the LOCKTABLE method.
Update	runtime version 1.0	All read operations are performed with REPEATABLE READ locking until the table is either modified by any write operation or locked with the LOCKTABLE method.
Snapshot	runtime version 1.0	ll read operations are performed with REPEATABLE READ locking.
Browse	runtime version 1.0	All read operations are performed with READ UNCOMMITTED locking.
Report	runtime version 1.0	Maps to the Browse transaction type.

Remarks

There are four basic transaction types: Browse, Snapshot, UpdateNoLocks, and Update. Additionally, there is a Report type that maps to the Browse transaction type. Each transaction type defines the behavior of a transaction in Dynamics 365 Business Central and takes effect from the start of a transaction. A transaction starts at the start of the outermost code or immediately after the Commit Method (Database) is called. A transaction ends at the end of the outermost code or when the Commit method is called. For example, if a method in a codeunit calls another codeunit, then a new transaction is not started at the start of the second codeunit.

The following table shows transaction behavior with SQL Server.

Transaction Type	Behavior
Browse	This is a read-only transaction. Modifications cannot occur within the transaction. All read operations are performed with READ UNCOMMITTED locking. Therefore, no locks are added and locks that are added by other sessions are not honored. This means that the transaction may read uncommitted data. For more information about READ UNCOMMITTED locking, see SET TRANSACTION ISOLATION LEVEL (Transact-SQL) in the MSDN Library.
Snapshot	This is a read-only transaction. Modifications cannot occur within the transaction. All read operations are performed with REPEATABLE READ locking. Therefore, shared locks are added on all data and are maintained until the end of the transaction. This prevents other transactions from modifying any rows that have been read by the current transaction. For more information about REPEATABLE READ locking, see SET TRANSACTION ISOLATION LEVEL (Transact-SQL) in the MSDN Library.
UpdateNoLocks	This is an update transaction. Modifications can occur within the transaction. All read operations are performed with READ UNCOMMITTED locking until the table is either modified by a write operation or locked with the LockTable Method (Record). From this point until the end of the transaction, all read operations are performed with UPDLOCK locking. For more information about UPDLOCK locking, see Table Hints (Transact-SQL) in the MSDN Library. This transaction type improves concurrency for all tables that users access within the transaction by delaying locking as much as it can. However, the disadvantage is that you must know when to lock the tables for the required transaction behavior. This is the default transaction type if you have not specified a type with the CurrentTransactionType Method (Database).
Update	This is an update transaction. Modifications can occur within the transaction. All read operations are performed with REPEATABLE READ locking until the table is either modified by any write operation or locked with the LockTable method. From this point forward, all read operations are performed with UPDLOCK locking. This transaction type provides full transaction isolation from the start of the transaction, regardless of the lock status of tables that users access within the transaction.

Note

In earlier versions of Dynamics 365 Business Central, the Snapshot and Update transaction types performed read operations with SERIALIZABLE locking until the table was either modified by a write operation or locked with the LockTable method. In Dynamics 365 Business Central, these transaction types perform read operations with REPEATABLE READ locking until the table is either modified by a write operation or locked with the LockTable method.

Phantom reads cannot occur with SERIALIZABLE locking because the filter range is locked instead of the records. Phantom reads can occur with REPEATABLE READ locking because only the records are locked. You should know this difference when you upgrade from an earlier version to Dynamics 365 Business Central. For more information about phantom reads, see Concurrency Effects in the MSDN Library.

Report and XMLport objects have a TransactionType property, which you can view and modify in the Properties window. The TransactionType property that is specified on a report or XMLport object is used only when you run the report or XMLport from Object Designer.

See Also

Isolation Levels in the Database Engine
CurrentTransactionType Method (Database)