Concurrency Control in Distributed Database Systems with Read-Only replication

Anne Denton and Vijayakumar Shanmugasundaram

Distributed Systems Multiple databases that behave as

one Replication

Speeds up “read” Slows down “write”

Problem: compromises local loads Can we restore autonomy of

databases?

Idea Databases have r/w section with local

locking Data from other databases is replicated

in a read-only section Read-only data is “validated” after all

reads and writes and before commit If validation fails => abort => optimistic treatment of replicated

data

How validate? Request validation only of items to

be read? Rather: send validation information

for entire replicated section (similar to request vector)

Compression? => P-trees

Concurrency Control Define new operations and check

serializability with existing r, w Validate Reload Read

Read-only transactions don’t require validation, if multi-version CC and virtual commit-time is used

Design Choices Validate also at beginning of

transaction? Download invalidated data

automatically? Effect on read-write transactions Effect on read-only transactions

Regular validity checks?

Simulation Using OOD Java JCL and Our own Classes Implementation of P-tree? Accommodation of any design

choices Results Analysis – University

Statistician