Neoview JDBC Type 4 Driver Programmer's Reference (R2.2, R2.3, R2.4, R2.5)

LOB Architecture: Tables for LOB Data Support
Setting Properties for the LOB Table
Before running the JDBC application that uses BLOB and CLOB data through the JDBC API, the
database administrator must create the LOB tables. For information on creating LOB tables, see
“Managing LOB Data by Using the Lob Admin Utility” (page 60).
The JDBC applications that access BLOB or CLOB data must specify the associated LOB table
names and, optionally, configure the reserveDataLocators property.
Specifying the LOB Table
At run time, a user JDBC application notifies the Type 4 driver of the name or names of the LOB
tables associated with the CLOB or BLOB columns of the base tables being accessed by the
application. One LOB table or separate tables can be used for BLOB and CLOB data.
The JDBC application specifies a LOB table name either through a system parameter or through
a Java Property object by using one of the following properties, depending on the LOB column
type:
Property nameLOB Column Type
blobTableNameBLOB
clobTableNameCLOB
For more information about using these properties, see “LOB Table Name Properties” (page 43).
Reserving Data Locators
A data locator is the reference pointer value (SQL LARGEINT data type) that is substituted for
the BLOB or CLOB column in the base table definition. Each object stored into the LOB table is
assigned a unique data locator value. Because the LOB table is a shared resource among all
accessors that use the particular LOB table, reserving data locators reduces contention for getting
the next value. The default setting is 100 reserved data locators; therefore, each JVM instance can
insert 100 large objects (not chunks) before needing a new allocation.
Specify the number of data locators (n) to reserve for your application by using the Type 4 driver
property hpt4jdbc.reserveDataLocators. For information about specifying this property,
see “reserveDataLocators Property” (page 46).
Storing CLOB Data
Store CLOB data in these ways:
• “Inserting CLOB Columns by Using the Clob Interface” (page 53)
• “Writing ASCII or MBCS Data to a CLOB Column” (page 53)
52 Working with BLOB and CLOB Data