Sometimes when you change the DNS for your domain, it may take upto 24 hours to actually reflect the DNS to your your domain, but when you migrate your website from one hosting provider to another hosting provider, you need to know which are the actual DNS settings effectively getting used for your website in current time.
Lot of confusion also starts when you have multiple subdomains and only few of the subdomains are hosted to another hosting provider and some one to other. In this case, knowing which subdomain is using which DNS using A record is important.
This can be checked from using web based equivalent of Dig command using Google Admin ToolBox.
To check DNS and related records, open https://toolbox.googleapps.com/apps/dig/ and enter your domain name and click on the type of record you want to check.
For example, below image shows the TXT records for our this website.