BLOBs and CLOBs

InterSystems SQL supports the ability to store BLOBs (Binary Large Objects) and CLOBs (Character Large Objects) within the database as stream objects. BLOBs are used to store binary information, such as images, while CLOBs are used to store character information. BLOBs and CLOBs can store up to 4 Gigabytes of data (the limit imposed by the JDBC and ODBC specifications).

The operation of the BLOBs and CLOBs is identical in every respect except how they handle character encoding conversion (such as Unicode to multibyte) when accessed via an ODBC or JDBC client: the data in a BLOB is treated as binary data and is never converted to another encoding while the data in a CLOB is treated as character data and is converted as necessary.

If a binary stream file (BLOB) contains the single non-printing character $CHAR(0), it is considered to be an empty binary stream. It is equivalent to the "" empty binary stream value: it exists (is not null), but has a length of 0.

From the object point of view, BLOBs and CLOBs are represented as stream objects. For more information, see the chapter “Working with Streams” of Defining and Using Classes.