difference between checkpoint_segments and wal_keep_segments in postgres configuration file

[Raghavendra Rao J S V <raghavendrajsv@xxxxxxxxx>]

I am not clear the difference between  checkpoint_segments and wal_keep_segments .

I would like to now below things. Please explain.Thanks in advance.

• Difference  between checkpoint_segments and wal_keep_segments value 
• Role  of  checkpoint_segments and wal_keep_segments 
• Which one should has higher value.
  

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Regards,
Raghavendra Rao J S V