  In order to increase availability in a distributed system some or all of the
data items are replicated and stored at separate sites. This is an issue of key
concern especially since there is such a proliferation of wireless technologies
and mobile users. However, the concurrent processing of transactions at
separate sites can generate inconsistencies in the stored information. We have
built a distributed service that manages updates to widely deployed
counter-like replicas. There are many heavy-weight distributed systems
targeting large information critical applications. Our system is intentionally,
relatively lightweight and useful for the somewhat reduced information critical
applications. The service is built on our distributed concurrency control
scheme which combines optimism and pessimism in the processing of transactions.
The service allows a transaction to be processed immediately (optimistically)
at any individual replica as long as the transaction satisfies a cost bound.
All transactions are also processed in a concurrent pessimistic manner to
ensure mutual consistency.
