Replication Server maintains transaction serialization in parallel DSI by committing transactions at the replicate database in the same order in which they were committed at the primary database. When using more than one DSI thread to process transactions, Replication Server can execute operations in a different order at the replicate database as long as the order of processing does not result in conflicting updates. The commit order at the primary and replicate databases always matches; the execution or processing order at the replicate database may or may not match.
Replication Server provides four different serialization methods for minimizing update conflicts. The serialization method you choose depends on the amount of contention you expect between parallel threads and your replication environment. Each serialization method defines how much of a transaction can start before it must wait for the previous transaction to commit.
The serialization methods are:
no_wait
wait_for_start or none
wait_for_commit
single_transaction_per_origin
Use the alter connection command with the dsi_serialization_method parameter to select the serialization method for a database connection. For example, enter the following command to select the wait_for_commit serialization method for the connection to the pubs2 database on the SYDNEY_DS data server:
alter connection to SYDNEY_DS.pubs2 set dsi_serialization_method to 'wait_for_commit'
Non-Sybase data servers may not support the functionality
of the isolation_level_3 method.
However, you can alter its associated function string, rs_set_isolation_level3,
to accommodate the non-Sybase data server.
We can describe a transaction as containing three parts:
The beginning
The body of the transaction, consisting of operations such as insert, update, or delete
The end of the transaction, consisting or a commit or a rollback
While providing commit consistency, the serialization method defines whether the beginning of the transaction waits for the previous transaction to become ready to commit or if the beginning of the transaction can be processed as soon as possible.
