Are you importing/exporting data from ODBC or using ESS with a shadow table?
I can find this reference in my Known Bugs List, but the original poster indicates a limit of 8192 characters instead of 4090.
For More Information see: External Data Source Text Field Truncated to 8192 chars when viewed in layout field.
This is one of many acknowledged bugs that can be found in the Known Bug List thread here in the Report an Issue section of the forum.
It can also be downloaded as a database file from: https://www.dropbox.com/s/jt09b82i0xijbu3/FMP%20Bugs.zip
I have encountered the same issue with FileMaker ODBC driver 12.3.103a (32bit).
In my case, however, the text is truncated to around 1365(= 4096/3) characters
I think it is because the raw data is UTF-8 and the UTF-8 text is then converted to Unicode.
I am using C# and here is a sample code:
using (var conn = new System.Data.Odbc.OdbcConnection("DSN=TestDSN;UID=Admin;PWD=password"))
using (var cmd = conn.CreateCommand())
cmd.CommandText = "SELECT Field1 FROM Table1";
using (var reader = cmd.ExecuteReader())
var txt= reader.GetString(0);
var tl = txt.Length;//truncated to about 1365
What is worse in my environment, depending on the text data, the system can hang!
(Of course, I have set the Use Long Varchar option in the ODBC panel to YES.)
I am sure this is a bug of the FileMaker ODBC driver, and I hope they will fix this bug as soon as possible.