Managing Multiple Isolation Levels in Middleware Database Replication Protocols

Abstract

Many database replication protocols have been designed for guaranteeing a serialisable isolation level, since it is appropriate for almost all applications. However, it also requires a tight coordination among replicas and might generate high abortion rates with some workloads. So, other isolation levels have also been considered, such as snapshot isolation and cursor stability, but none of the previous works has proposed an overall support for more than one isolation level at the same time. This paper explores such a research line.

Supporting Multiple Isolation Levels in Replicated Environments.

“…The results presented here summarize and extend our previous works in [11], [53], [7], [10] and [9]. The problem is identified in [11], later pointed in [16] as one of the existing challenges in database replication.…”

“…The problem is identified in [11], later pointed in [16] as one of the existing challenges in database replication. In [11] we also explain how existing replication protocols may be extended to include multiple isolation levels support.…”

“…The problem is identified in [11], later pointed in [16] as one of the existing challenges in database replication. In [11] we also explain how existing replication protocols may be extended to include multiple isolation levels support. It also informally suggests how concrete PL-1, PL-2, PL-2.99 and PL-3 levels [2] can be supported and presents an example protocol.…”

“…Some of our previous works [11,53] present specific protocols that support several isolation levels simultaneously ( [53] includes some empirical results). However, these papers do not present a general solution, nor do they formally demonstrate the correctness of their proposals.…”

“…Before the execution of a transaction, one of the supported replication protocols is selected based on the transaction requirements. This approach is more modular and general than [11,53] since isolation is only one possible criterion to match a protocol to a given transaction. However, sometimes modifying an existing and implemented protocol is a more straightforward solution than deploying a meta-protocol and developing at least one protocol per supported isolation level.…”