JDBC Type 2 Driver Programmer's Reference for SQL/MX Release 3.2.1 (H06.26+, J06.15+)

Figure 2 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 JDBC/MX Lob Admin Utility” (page 55).
The JDBC applications that access BLOB or CLOB data must specify the associated LOB table
names and, optionally, configure the reserveDataLocator property. These tasks are described
in the topics:
• “Specifying the LOB Table” (page 45)
• “Reserving Data Locators” (page 45)
Specifying the LOB Table
At run time, a user JDBC application notifies the JDBC/MX 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 26).
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.
By using a default setting of 100 reserved data locators, each JVM instance can insert 100 large
objects (not chunks) before needing a new allocation.
You can specify the number of data locators (n) to reserve for your application by using the
JDBC/MX system property jdbcmx.reserveDataLocators in the command line.
For information on specifying this property, see “Setting the reserveDataLocators Property” (page 42).
Setting Properties for the LOB Table 45