How to increase DBTEXTSIZE and DBTEXTSIZE.

Hello!

I need to fetch data from TEXT field.
But the data size of particular record is always 4096 (for data that
greater than 4kb)

int dataLength  = dbdatlen( conn, i + 1 );

I found (for db-lib) that need to increase options DBTEXTSIZE and
DBTEXTSIZE to solve this problem:
 
dbsetopt( conn, DBTEXTSIZE,  "2,147,483,647", -1 );

dbsetopt( conn, DBTEXTLIMIT, "2,147,483,647", -1 );

But these function return FAIL, and have no affect. The returned length
still 4096.

Is any other way in to fetch big data (text, varchar, varbinary...)?

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Best Regards!