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Version: 18


Allows the actions in the REST request to be in a transaction. If there are no errors, the transaction is validated. Otherwise, the transaction is cancelled.


When you have multiple actions together, you can use $atomic/$atOnce to make sure that none of the actions are completed if one of them fails. You can use either $atomic or $atOnce.


We call the following REST request in a transaction.

POST /rest/Employee?$method=update&$atomic=true

POST data:

"__KEY": "200",
"firstname": "John"
"__KEY": "201",
"firstname": "Harry"

We get the following error in the second entity and therefore the first entity is not saved either:

"__STATUS": {
"success": true
"__KEY": "200",
"__STAMP": 1,
"uri": "/rest/Employee(200)",
"__TIMESTAMP": "!!2020-04-03!!",
"ID": 200,
"firstname": "John",
"lastname": "Keeling",
"isWoman": false,
"numberOfKids": 2,
"addressID": 200,
"gender": false,
"address": {
"__deferred": {
"uri": "/rest/Address(200)",
"__KEY": "200"
"__ERROR": [
"message": "Cannot find entity with \"201\" key in the \"Employee\" dataclass",
"componentSignature": "dbmg",
"errCode": 1542

Even though the salary for the first entity has a value of 45000, this value was not saved to the server and the timestamp (__STAMP) was not modified either. If we reload the entity, we will see the previous value.