The maximum size of a VARCHAR column is user-defined. If the inserted data is larger than this, an exception is thrown. The example below defines a table with a VARCHAR(100) column, which limits the size to 100 characters.
CREATE TABLE T (ID INT, DATA VARCHAR(100))
You can use a database manager and execute the SCRIPT command to see all your table definitions and their column size. Alternatively, SELECT * FROM INFORMATION_SCHEMA.COLUMNS shows the characteristics of each column.
You can use the ALTER TABLE table_name ALTER COLUMN col_name SET DATA TYPE to increase the size of an existing column.