When migrating millions of Contact records and encountering the error "npsp.TDTM_Address: System.LimitException: Apex CPU time limit exceeded," you can take the following actions:

Disable Automation:

Go to NPSP Settings.

Navigate to "TDTM" (Table Driven Trigger Management).

Disable all automation triggers temporarily to ensure they do not interfere with the data load process.

Load Address Object Separately:

Split the data load into two parts: first load Contacts without address data, then load address data separately.

This reduces the complexity and processing required for each batch.

Disable ADDR_Addresses_TDTM Handler:

In NPSP Settings, go to "Trigger Configuration."

Locate the 'ADDR_Addresses_TDTM' handler.

Disable this specific handler to prevent it from executing during the data import process.

Reduce Batch Size:

When using Data Loader or any import tool, set the batch size to a significantly lower number (e.g., 100 or 200 records per batch).

This helps in managing CPU limits and ensures smoother processing.

By following these steps, you can mitigate the Apex CPU time limit issue and successfully import large volumes of data into NPSP.