There are a lot of examples in the pega OOTB rules, just search obj-open-by-handle in the designer studio, e.g., ExpressApp activity first step. Also check the online help: https://pdn.pega.com/sites/pdn.pega.com/files/help_v721/procomhelpmain.htm#engine/database/tables/eng-db-handle-usage-ref.htm#kanchor3562

Just search with the same text keeping "All Content", then many OOTB activities can be seen.

Ideally, it is used to open and modify the contents of Work Objects to some other values. After that do obj-save with write now for saving the contents to DB. 

Hi akash,

In order to use obj-open-by-handle. you need to obtain the pzInsKey of the object created.

it will generally be class name (work pool) and followed by Work object for example : LP7-HRMS-WORK O-1

To put it in simple terms, its the way you open a record using a key. Think of a data base query where you say something like Select * from SomeTable where Key='KeyValue'.

Its the same.

You may want to read, update or do something on a record in Pega - you use this call.