JDBC Type 4 Driver Programmer's Reference for SQL/MX Release 3.2.1

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.
• Similarly, when the application obtains the OutputStream or Writer from the LOB object,
the Type 4 driver closes the OutputStream or Writer that is already associated with the
LOB object.
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