# Optimistic locking differences between version 1 and version 2 of the SDK for Java
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Both V1 and V2 implement optimistic locking with an attribute annotation that marks one property on your bean class to store the version number.


**Differences in optimistic locking behavior**  

|  | V1 | V2 | 
| --- | --- | --- | 
| Bean class annotation | @DynamoDBVersionAttribute | @DynamoDbVersionAttribute (note that V2 uses a lowercase "b") | 
| Initial save | Version number attribute set to 1. | The starting value for the version attribute set with `@DynamoDbVersionAttribute(startAt = {{X}})`. Default value is 0. | 
| Update | The version number attribute is incremented by 1 if the conditional check verifies that the version number of the object being updated matches the number in the database. | The version number attribute is incremented if the conditional check verifies that the version number of the object being updated matches the number in the database.<br />The version number attribute incremented by the `incrementBy` option set with `@DynamoDbVersionAttribute(incrementBy = {{X}})`. Default value is 1. | 
| Delete | DynamoDBMapper adds a conditional check that the version number of the object being deleted matches the version number in the database. | V2 does not does not automatically add conditions for the delete operations. You must add condition expressions manually if you want to control the delete behavior.<br />In the following example `recordVersion` is the bean's version attribute.<pre>// 1. Read the item and get its current version.<br />Customer item = customerTable.getItem(Key.builder().partitionValue("someId").build());<br />AttributeValue currentVersion = item.getRecordVersion();<br /><br />// 2. Create conditional delete with the `currentVersion` value.<br />DeleteItemEnhancedRequest deleteItemRequest =<br />    DeleteItemEnhancedRequest.builder()<br />       .key(KEY)<br />       .conditionExpression(Expression.builder()<br />           .expression("recordVersion = :current_version_value")<br />           .putExpressionValue(":current_version_value", currentVersion)<br />           .build()).build();<br /><br />customerTable.deleteItem(deleteItemRequest);</pre> | 
| Transactional Write with a Condition Check | You cannot use a bean class that is annotated with @DynamoDBVersionAttribute in an addConditionCheck method. | You can use a bean class with the @DynamoDbVersionAttribute annotation in an addConditionCheck builder method for a transactWriteItems request. | 
| Disable | Disable optimistic locking by changing the DynamoDBMapperConfig.SaveBehavior enumeration value from UPDATE to CLOBBER. | Do not use the `@DynamoDbVersionAttribute` annotation. |