Understanding Transactional Integrity in X++

In X++, maintaining transactional integrity is crucial to prevent data corruption and ensure the system performs reliably under concurrent usage. If proper safeguards aren’t used, issues like inconsistent data and poor scalability can arise.

X++ provides two important internal mechanisms to help preserve transactional integrity:

1. forUpdate Check

Ensures that a record can only be updated or deleted if it was explicitly selected for update.
Use the forUpdate keyword in the select statement or the selectForUpdate() method on the table buffer to mark the record for update.

2. ttsLevel Check

Ensures that a record is updated or deleted within the same transaction scope in which it was selected for update.
This check prevents operations outside the appropriate transaction boundary.

Transaction Control Statements in X++

ttsBegin

Marks the start of a transaction. All data operations between ttsBegin and ttsCommit are treated as a single atomic unit. This helps ensure that partial updates don’t corrupt data.

ttsCommit

Ends and commits the current transaction. Once committed, changes are guaranteed to be persisted by the system.

ttsAbort

Rolls back all changes made in the current transaction, restoring the database to its previous state. Typically used when the user cancels the process or when a critical failure occurs.

Note It’s generally recommended to use exception handling (throw) instead of calling ttsAbort directly. A thrown exception will automatically roll back the current transaction.

Nested Transaction Example

X++ allows nested transactions. However, changes are only committed after the outermost ttsCommit is successfully executed.

				
					ttsBegin;
    // Outer transaction
    ttsBegin;
        // Inner transaction
    ttsCommit;
ttsCommit;

Practical Examples

Valid Update Using forUpdate and Transaction Block

				
					CustTable custTable;

ttsBegin;
    select forUpdate custTable where custTable.AccountNum == '5000';
    custTable.CustGroup = '1';
    custTable.update();
ttsCommit;

This code selects a customer record for update, modifies the CustGroup, and saves it—all within a transaction.

❌ Rejected by forUpdate Check (Missing forUpdate)

				
					ttsBegin;
    select myTable; // Error: Not selected for update
    myTable.myField = 'xyz';
    myTable.update();
ttsCommit;

The update is rejected because the record was not selected using forUpdate.

❌ Rejected by ttsLevel Check (Wrong Transaction Scope)

				
					ttsBegin;
    select forUpdate * from myTable;
    myTable.myField = 'xyz';
ttsCommit;

ttsBegin;
    myTable.update(); // Error: Update outside original transaction
ttsCommit;

The record is updated outside the transaction in which it was selected, violating the ttsLevel check.

Summary

To maintain data consistency and system reliability in X++, always:

Use forUpdate when modifying records.
Keep all select/update operations within the same transaction scope.
Use ttsBegin, ttsCommit, and throw for safe transactional control.