Salesforce DML: Order of Execution When a Row Lock Error Occurs in Master-Detail Relationships

Example Scenario: Object A (Master) and Object B (Detail)

Object A and Object B have a Master-Detail relationship. Object A is the Master and Object B is the Detail.

1. Record A is locked by Transaction 1.
2. Transaction 2 begins a new DML operation on Record B.
3. Salesforce loads Record B from the database (or initializes it for an upsert/insert operation).
4. Salesforce executes order-of-execution steps 1–15 for Record B Order of execution (triggers, validation rules, workflow rules, etc.).
5. At step 16, Salesforce internally attempts to acquire a lock on the parent Record A. Because Record A is already locked by Transaction 1, the lock cannot be placed immediately.
6. Record B waits up to 10 seconds for Salesforce to obtain a lock on Record A.

If the lock on Record A is released within 10 seconds: Salesforce acquires the lock on Record A and proceeds with order-of-execution steps 1–15 for Record A.

If the lock on Record A is NOT released within 10 seconds: Salesforce throws the "Unable to lock row — Record currently unavailable" error. The DML operation for Record B is rolled back to the previous savepoint (the state before the update or insert was attempted). Because an exclusive lock on Record A was never obtained, Order of execution steps 1–15 for Record A are also not executed.