JDBC Type 4 Driver 2.0 Programmer's Reference (SQL/MX 2.x)

Deleting BLOB Data
To delete BLOB data, the JDBC application uses the SQL DELETE statement to delete the row in the
base table.
When the row containing the BLOB column is deleted by the application, the corresponding BLOB data is
automatically deleted by the delete trigger associated with the base table. For information about triggers,
see Using SQL/MX Triggers to Delete LOB Data.
See also NULL and Empty BLOB or CLOB Value.
NULL and Empty BLOB or Empty CLOB Value
The data locator can have a NULL value if the BLOB or CLOB column is omitted in the insert statement.
The Type 4 driver returns NULL when the application retrieves the value for such a column.
When the application uses the EMPTY_BLOB() function or the EMPTY_CLOB() function to insert
empty BLOB or CLOB data into the BLOB or CLOB column, the Type 4 driver returns the Blob or Clob
object with no data.
Transactions Involving Blob and Clob Access
You must ensure that your JDBC applications control the transactions when the BLOB columns or CLOB
columns are accessed or modified. To control the transaction, set the connection to autocommit OFF
mode.
All LOB data access or modification is done under the application's transaction. When the autocommit
mode is ON and LOB data is accessed or modified, the Type 4 driver throws the SQLException,
Autocommit is on and LOB objects are involved.
Access Considerations for Clob and Blob Objects
The Type 4 driver allows all the valid operations on the current Clob object or Blob object, called a
LOB object. LOB objects are current as long as the row that contains these LOB objects is the current
row. The Type 4 driver throws an SQLException, issuing the following message, when the application
attempts to perform operations on a LOB object that is not current:
Lob object {object-id} is not current
Only one InputStream or Reader and one OutputStream or Writer can be associated with the
current LOB object.
When the application obtains the InputStream or Reader from the LOB object, the Type 4
driver closes the InputStream or Reader that is already associated with the LOB object.
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Similarly, when the application obtains the OutputStream or Writer from the LOB object,●