Need a ladge json collection which I can import into my mongodb database for checking oplog of replicaset working properly or not.
Hi @Sabbir_Sattar_Mukit - Welcome to the community 
Could you describe the goal you’re trying to achieve with regards to the oplog? Please also provide your MongoDB version. Note that the oplog is for internal MongoDB use and the format and content can and will change with no notice. If you need to monitor changes in a collection/database/deployment then the supported method is to use change streams instead.
Regards,
Jason