It is not required but it is highly recommended.  Since you are coming from an older version V2012, I would recommend it.  If you have any issues with your data updating to the new version V2019 then you will need to go back to V2012 and perform the rebuild.  You would need to uninstall v2019, reinstall V2012, restore your V2012 backup prior to starting the conversion, rebuild your data in V2012.  Next, re-install V2019 and start your update again.

Sincerely,

Coleen

Follow the steps to upgrade, rushing will cost more time in the end if there are problems. The re-build is there to root out problems early. Have MULITPLE backups just in case. You will be doing a database upgrade per company with the upgrade.

If a speed up is required, if you have multiple BW companies, choose to be in the smallest company ( based on hard drive size used), it will quicken up the initial install, and then you will be allowed to upgrade the remaining companies databases in batch.  This will give you time to start upgrading the clients while the databases are converted.

When its time to replace the Server that BW is on, pay special attention to the CPU choice  and the per core speed  and hard drive/SSD sub-systems. I like the Intel 6 core+ processors and RAID 5 or 6 with 4 or more drives,  using  Solid state enterprise class drives. - Our rebuild times for 1 GB company is under 10 minutes for GL AP AR IC OE - the month end close is under 3 minutes with  3 years of data