Update On Large Table - Change Data Type For Text Column

I need to update a large table, about 55 million rows, without filling the transaction log, in the shortest time as possible. The goal is to alter the table and change the data type for Text column from VARCHAR(7900) to NVARCHAR(MAX).

Since I cannot do it with an ALTER TABLE statement (it would fill up the transaction log) I'm thinking to:

- rename column Text in Text_OLD
- add Text column of type NVARCHAR(MAX)
- copy values in batches from Text_OLD to Text

The table is defined like:

create table DATATEXT(
rID INTEGER NOT NULL,
sID INTEGER NOT NULL,
pID INTEGER NOT NULL,
cID INTEGER NOT NULL,
err TINYINT NOT NULL,

[Code] ....

I've thought about a stored procedure doing this but how to copy values in batch from Text_OLD to Text.

The code I would start with (doing just this part) is the following, but maybe there are more efficient ways to do it, or at least there's a better way to select @startSeq in the WHILE loop (avoiding to select a bunch of 100000 sequences and later selecting the max).

declare @startSeq timestamp
declare @lastSeq timestamp
select @lastSeq = MAX(sequence) from [DATATEXT] where [Text] is null
select @startSeq = MIN(Sequence) FROM [DATATEXT] where [Text]is null
BEGIN TRANSACTION T1
WHILE @startSeq < @lastSeq

[Code] ....