SyncModel
The sync  parameter defines how layers can be synced. When creating a replica, clients can choose one of the following sync models by setting the sync  parameter:
- per—Layers within a replica cannot be synchronized independently. Each- Replica - synchronizeoperation applies to all the layers in the replica.- Replica 
- per—Layers within a replica can be synchronized independently. A chosen subset of the layers within a replica can be synchronized when running the- Layer - synchronizeoperation.- Replica 
The feature service’s sync  property describes the supported sync models.
"syncCapabilities": {
  "supportsPerLayerSync": true,
  "supportsPerReplicaSync": true,
}For example, if supports  is true  and supports  is false , you can choose only a per  sync model when running the Create Replica operation. If supports  is not provided, it's false  by default. If supports  is not provided, it's true  by default.
RollbackOnFailure
When synchronizing, clients can set the rollback  parameter. Rollback  determines the behavior when there are errors while importing edits on the server during synchronization. This only applies in cases where clients are uploading edits to the server.
Rollback  can be set as follows:
- true—If an error occurs while importing edits on the server, all edits are rolled back (not applied), and the operation returns an error in the response. Use this setting when the edits are such that you either want all or none applied.
- false—If an error occurs while importing an edit on the server, the import process skips the edit and continues. All edits that were skipped are returned in the results with information describing why they were skipped.
The feature service’s sync  property determines if the synchronizeReplica operation's rollback  parameter is supported.
"syncCapabilities": {
  "supportsRollbackOnFailure": <true | false>
}If the supports  property is true , you can set the rollback  parameter to true  or false  when running the synchronizeReplica operation. If the supports  property is false , the synchronizeReplica operation does not support the parameter.
When supports  is false  and only a per  sync model is supported (supports  set as true  and supports  set as false ), synchronizeReplica always applies the false rollback  behavior above.
When supports  is false  and only a per  sync model is supported (supports  set as false  and supports  set as true ), synchronizeReplica always applies the true rollback  behavior above.
For information on how to handle errors during sync, see Error handling with sync operations.
Supported rollbackOnFailure behavior and sync models
The following table lists the supported sync  and rollback  behavior with ArcGIS Server:
| Data source | rollbackOnFailure | PerLayer syncModel | PerReplica syncModel | 
|---|---|---|---|
| Nonversioned data | False | Yes | No | 
| Versioned data | True | No | Yes |