# 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. 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. 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.  |