Replication Guide and Reference
Mobile replication requirements center around having copies of centrally
located tables on mobile clients. Special considerations arise with this
approach, primarily from the need for the target site to initiate and control
the replication operation. IBM Replication supports mobile replication
requirements in the following ways:
- On-demand execution of the Capture and Apply programs - In an
unpredictable mobile environment, the mobile client must initiate and control
the connections. To reduce communication costs, the duration of phone
connections must be minimized and the mobile client is not continuously in
operation. The Capture and Apply programs must operate only for the duration
within which all the accumulated transactions are captured and copied to or
from the centrally located tables. When the replication sources and
subscriptions are defined on the mobile client, the Capture and Apply programs
are independent of all other IBM Replication components. They can be run in an
on-demand mode whenever required to dynamically connect to the target site.
- Push and pull options - If you must upload new or changed data
from the mobile clients to the replication source site, the Apply program on
the mobile client automatically pushes the data to the replication source
site.
- Changed data retention - Because of unpredictable connection
arrangements, you must ensure that all changed data is retained until each of
the mobile clients has replicated its data. The best way to configure IBM
Replication for optimized data retention is to use a CCD table, and possibly
locate it on a staging server. Two Apply programs are needed. One Apply
program moves the data from the CD and UOW tables to a CCD table so that the
Capture program can prune the changed data on a regular basis. Another Apply
program, on an intermediate server, moves the data from the CCD table to the
mobile client. This configuration is not available for update-anywhere
replication.
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