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<chapter id="failover">

<title>Failover, Replication, Load Balancing, and Clustering Options</title>

is because each server operates independently, and because SQL

queries are broadcast (and not actual modified rows). If this

is unacceptable, applications must query such values from a

single server and then use those values in write queries. Also,

care must be taken that all transactions either commit or abort

on all servers Pgpool is an example of this type of replication.

single server and then use those values in write queries.

Also, care must be taken that all transactions either commit

or abort on all servers, perhaps using two-phase commit (<xref

linkend="sql-prepare-transaction"

endterm="sql-prepare-transaction-title"> and <xref

linkend="sql-commit-prepared" endterm="sql-commit-prepared-title">.

Pgpool is an example of this type of replication.

</para>

</listitem>

</varlistentry>