3. Planning Your Replication Scheme : Replication Scheme Examples : Example: R.E.P. CDDS 0
 
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Example: R.E.P. CDDS 0
The Company’s main CDDS (CDDS 0) is shared by its offices in New York City, San Francisco, Dallas, London, and Hong Kong. New York, London, and Hong Kong are full peers in this CDDS. San Francisco is a protected read-only target, and Dallas is an unprotected read-only target. The following table illustrates the database information on the CDDS Worksheet for this CDDS:
Database Number/Name
Target Type
Server Number
10 nyc::hq
1 (full peer)
1
11 sfo::west
2 (protected read-only)
4
12 dal::central
3 (unprotected read-only)
4
20 lon::europe
1 (full peer)
2
30 hkg::asia
1 (full peer)
3
New York acts as the U.S. hub and distributes data to San Francisco, Dallas, and London. London acts as the international hub and sends data to New York and Hong Kong. San Francisco is the U.S. alternate site and has a redundant path from Hong Kong.
The Company’s CDDS Diagram for CDDS 0 looks like this:
The Company’s Propagation Path entries on the CDDS Worksheet for CDDS 0 are listed in the following table:
Originator DB
Local DB
Target DB
Comment
10
10
11
NYC to SFO
10
10
12
NYC to DAL
10
10
20
NYC to LON
10
20
30
NYC to HKG through LON
10
30
11
NYC to SFO through LON and HKG
20
20
10
LON to NYC
20
20
30
LON to HKG
20
30
11
LON to SFO through HKG
20
10
12
LON to DAL through NYC
20
10
11
LON to SFO through NYC
30
30
11
HKG to SFO
30
30
20
HKG to LON
30
20
10
HKG to NYC through LON
30
10
11
HKG to SFO through LON and NYC
30
10
12
HKG to DAL through LON and NYC
Because the San Francisco database has a redundant path, it has collisions when the same transaction arrives from both New York and Hong Kong. The Company handles this situation by using the collision mode BenignResolution, which resolves collisions that have the same transaction ID.