Dividing data from one table to multiple storage
Create a new table Table_A_Archive with exactly the same schema as Table_A_Changes.  Partition both these tables by, say, one-month date ranges.  As data becomes stale in Table_A_Changes swap that partition out and swap it into Table_A_Archive.  Your data retention policy can be efficiently enforced this way, too.

A view which unions the two tables can make querying simpler.