IBM Licensed Programs: Database Products 537
IBM Licensed Programs: Database Products
Replicating DATALINK Values
Accessing large files (such as multimedia data) over a remote network can be inefficient and
costly. If these files do not change, or change infrequently, faster access to the files and
reduced network traffic can be provided by replicating these files to remote sites. DB2
Universal Database provides a DATALINK data type that allows the database to control
access, integrity, and recovery for these kinds of files. DB2 Universal Database supports
DATALINK values on all platforms except OS/390.
Because external files can be very large, there must be sufficient network bandwidth for both
the Apply program and whatever file-transfer mechanism is used to copy these files. Likewise,
the target system must have sufficient disk space to accommodate these files.
Features Added to Improve Performance
• The DPRVSN parameter allows the specification of which version of the control tables
to create: Version 5 or Version 7.
• The STRDPRCAP command has a new parameter, GENCDROW. The GENCDROW
parameter is equivalent to the CHGONLY parameter that is used on the other
platforms. It provides the ability to specify that only changed columns are replicated.
• The STRDPRAPY command has two new parameters: DELAY and RTYWAIT. The
DELAY parameter specifies the time delay (in seconds) at the end of each Apply
program cycle when continuous replication is used. RTYWAIT specifies in seconds
how long the Apply program should wait after it encounters an error before it retries
the operation that failed. This allows operators to fix a problem encountered before
continuous replication is resumed.
• For replication scenarios where the target tables reside on the same AS/400 system
as the Change Data tables, the Version 7.1 Apply/400 code no longer resorts to the
use of spill files. This results in a significant performance gain. Users of the remote
journal set-up are the primary beneficiaries of this performance enhancement.
AS/400 Replication Extensions
• Remote Journal: DB2 DataPropagator Version 7.1 can now use the remote journal
function. The
Capture
component can now capture changes from a journal setup for
remote journal. Journal receivers are replicated to another system by the operating
system function of the remote journal. The
Apply
component is modified to access the
actual source to a staging area that eliminates work file processing.
• Relative Record Number Support: This function is added to DB2 DataPropagator
Version 7.1 to address the problem where a unique key could not be found for a copy
table. It allows a user to have a unique key for CCD and Point-in-time target tables
when no combination of target columns is unique.
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