# Data Retention

Data retention policy can be realised by TStorage using special USConnector command - **DELETE**.
It deletes data by key ranges (keyMin, keyMax). **DELETE** removes whole partitions - key range is rounded to partitions boundaries.

## Description

Only whole partitions are deleted. i.e., those fully covered by the **DELETE** key range.
If the key range does not cover the whole key range that logically belongs to a given 
partition, the partition is not deleted.
PUTs are not allowed within key range, for which deletion is pending. Otherwise, interleaved PUTs and DELETEs may corrupt range
partition.

### Usage
1. Client that executes deletion can connect only to a USConnector which resides on the same machine as Client.
2. Unblock deletion (reference to commandserver.py usage) on the USConnector.
3. Perfrom **DELETE** request on the USConnector.
4. Block deletion on the USConnector.

## **DELETE** Command

To use this command, one has to enable it on the USConnector first.

### **DELETE Request**

<figure align="center">
    <img src="/_static/img/delete_request.png">
</figure>

cmd \= 4

size \= size of KeyRange

### **DELETE Response \- SUCCESS**

<figure align="center">
    <img src="/_static/img/delete_response.png">
</figure>

result \= 0

size \= size of KeyRange

USConnector sends back key range that was taken into account while deleting.

### **DELETE Response \- ERROR**

<figure align="center">
    <img src="/_static/img/delete_response_error.png">
</figure>

result \= 1

size \= 0