Post Migration error in sql server error log
Those messages indicate checkpoint activity is occurring.  Checkpoints in SQL Server 2012 occur frequently, depending on several configuration variables, and are typically not something to be overly concerned about.

Check the recovery interval for your server:

SELECT c.name
    , c.value_in_use
FROM sys.configurations c
WHERE c.name = 'recovery interval (min)';


From the Microsoft Docs:


  The default recovery-interval value is 0, which allows the Database Engine to automatically configure the recovery interval. Typically, the default recovery interval results in automatic checkpoints occurring approximately once a minute for active databases and a recovery time of less than one minute. Higher values indicate the approximate maximum recovery time, in minutes. For example, setting the recovery interval to 3 indicates a maximum recovery time of approximately three minutes. 


What is your recovery time set to?  Are you experiencing poor performance?