Hi,
Recovery mechanism is the feature in DS to restart the job from point of failure.
1) If there is a DB crash, we have to use DB recovery mechanism.
2) If there is a ETL Job crash, we have to recovery the ETL job using
A) Manual Recovery
B) Automatic Recovery
A)To set-up manual recovery mechanism, we requires bellow artefacts.
1) ETL process table, table with Recovery_Flag name.
2) Global variable
3) Status Script to understand weather recovery is needed ot not
4) Conditional Work Flow
5) Then put your DataFlow with in a Try-Catch blosk
6) In Catch make enable all exception and provide the Fail Exception Script
7) Then go for else part as a DataFlow
B) We can set-up automatic recovery mechanism by providing bellow details
1) At JOB LEVEL
---> When you are executing the JOB, select "Enable Recovery" Check-box.
---> For failed job enable "Enable from last failed execution" check-box.
2) At WORK FLOW Level
---> Right click on Work-Flow and select "Recovery as a unit" check-box from the "Properties" of work-flow.
3) At DATA FLOW Level
---> Uncheck "Execute only once" if selected from the Data Flow "Properties"
Please check and reply 
Regards,
Sabat