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J.E. Armendáriz-Íñigo , F.D. Muñoz-Escoí {armendariz, fmunyoz}@iti.upv.es

Developing Flexible Database Replication Protocols: How to Integrate SI Replicas with Several Data Consistency Levels?. J.E. Armendáriz-Íñigo , F.D. Muñoz-Escoí {armendariz, fmunyoz}@iti.upv.es Instituto Tecnológico de Informática, Valencia, Spain

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J.E. Armendáriz-Íñigo , F.D. Muñoz-Escoí {armendariz, fmunyoz}@iti.upv.es

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  1. Developing Flexible Database Replication Protocols: How to Integrate SI Replicas with Several Data Consistency Levels? J.E. Armendáriz-Íñigo, F.D. Muñoz-Escoí {armendariz, fmunyoz}@iti.upv.es Instituto Tecnológico de Informática, Valencia, Spain J.R. Juárez-Rodríguez, J.R. González de Mendívil, J.R. Garitagoitia {jr.juarez, mendivil, joserra}@unavarra.es Universidad Pública de Navarra, Pamplona, Spain

  2. Concert Ticket Concert Ticket Concert Ticket Concert Ticket Concert Ticket Concert Ticket Database Replication - What is database replication? - Why database replication? * High Availability * Performance - Does database replication come “for free”?

  3. Cash Withdrawal Data Consistency Bank Database Account Balance: $1000 Give me $1000 Account Balance: $0 Bill Give me $800 Account Balance: $200 Cash Withdrawal Lucy Account Balance: $??????

  4. Data Consistency Levels Featured by Replication Protocols • Replication Protocols order transactions by way of the total-order message delivery featured by Group Communication Systems. • If we have DBMS replicas with serializable transaction isolation level: • One Copy Serializability (1CS): • The strongest correctness criterion. • The interleaved execution of a transaction is equivalent to a serial execution in a centralized setting. • If we have SI DBMS replicas: • It is not straightforward to see the “latest” version. • Generalized Snapshot Isolation • Transactions may use an older snapshot instead of the latest one of SI (i.e. the one of the delegate replica). • One Copy Snapshot Isolation (1CSI): • Transactions must remain block for reading from the latest snapshot version in a replicated environment. • Sending a total order message at the beginning of the transaction. • It looses the advantage of conventional SI where read operations never block.

  5. k-Bound GSI • Our aim is to define a function that measures the distance between • The start of the transaction (T.start) • The delivery of the start message (T.begin) • d(T.start, T.begin) < k • k > 0: Bound vakues for GSI level • k = 0: SI level • k = -1: Serializable level • k =: GSI level. • In order to define such distance we have multiple possibilities: • Time, overall PC-WS –even not colliding–, number of colliding items in each writeset, number of times an item.

  6. Developing Flexible Database Replication Protocols: How to Integrate SI Replicas with Several Data Consistency Levels? J.E. Armendáriz-Íñigo, F.D. Muñoz-Escoí {armendariz, fmunyoz}@iti.upv.es Instituto Tecnológico de Informática, Valencia, Spain J.R. Juárez-Rodríguez, J.R. González de Mendívil, J.R. Garitagoitia {jr.juarez, mendivil, joserra}@unavarra.es Universidad Pública de Navarra, Pamplona, Spain

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