A BLOB object possesses a BLOB value and a number of attributes.
BLOB values are stored in “normal tables” via the REF values. Direct storage is not possible. This has the advantage that you can execute all the habitual SQL operations with REF values in base tables. This would not be possible with BLOB values.
The attributes of a BLOB object are initially assigned the default values for the class when a BLOB object is created. The class defaults are defined with mime_clause, usage_clause and alphanumeric_literal when the BLOB table is created.
These attributes are identified by the names (tags) MIME and USAGE. Alongside these optional attributes, the time of creation and last modification are recorded by means of the CREATED and UPDATED tags. You can replace the MIME and USAGE attributes by means of the CLI call SQL_BLOB_TAG_PUT.
You use SESAM-CLI calls to create, read and set BLOB objects and values. However, you do not edit the content of BLOB values in SESAM/SQL but in object-specific programs. To transfer BLOB values from SESAM/SQL to another system, for example to BS2000, you can use one of two methods:
The BLOB value can be read in a single step with SQL_BLOB_VAL_GET.
You can use the command sequence SQL_BLOB_VAL_OPEN, SQL_BLOB_VAL_FETCH and SQL_BLOB_VAL_CLOSE to read the BLOB value sliceby-slice (see section “SESAM-CLI”).
Because of their size, you should delete any BLOB objects you no longer require.