RELATIONAL FAULT TOLERANT INTERFACE TO HETEROGENEOUS DISTRIBUTED DATABASES Prof. Osama Abulnaja...

RELATIONAL FAULT TOLERANT INTERFACE TO HETEROGENEOUS

DISTRIBUTEDDATABASES

Prof. Osama Abulnaja Afraa Khalifah

1103999

ContentIntroduction.The General Structure of The Model.Extended RPC Model.The Structure of The Basic Elements of the Model. View Generator. (UFI) User Friendly Interface. The Client Stub - Optimal Access plan generation. Server Stub - AMI and AMU The Structure of The CatalogFault-Tolerant Aspects and Recovery.Conclusion.

IntroductionPaper focus on the problem of heterogeneous distributed databases.Paper propose an uniform logical interface to the end user from a collection of different environments. Fault tolerance aspects of reliability of this system as well as error detection techniques and recovery protocols are also described.Problems due to heterogeneity :

o Interconnection o Filing o User interface

The General Structure of The Model• illustrates extended RPC model and how it works

CLIENT

• UFI (User Friendly Interface)

CLIENT STUB• DBMS process• Access Plan

generator• Query

processing• Code

Generation

TRANSPORT TRANSPORT

SERVER STUB

AMI

SERVER

AMU

CATALOG

call return call return

call

Return(Local Procedure Call)


(Remote Procedure Call)


CLIENT



generator• Query

processing• Code

Generation

TRANSPORT TRANSPORT

SERVER STUB

AMI

SERVER

AMU

CATALOG


call




• Receives user's queries.• Queries are passed to the lexical

analyzer and parser which transform them into parse tree form.


CLIENT



generator• Query

processing• Code

Generation

TRANSPORT TRANSPORT

SERVER STUB

AMI

SERVER

AMU

CATALOG


call




• receives queries into parse tree form and transfers them to the optimal access plan generation and code generation modules.

• This code contains calls to the procedures which can reside to other systems.

• Responsible also for translating the arguments into a suitable format for transmission over the network

• Generating code must be linked before calling one another.


CLIENT



generator• Query

processing• Code

Generation

TRANSPORT TRANSPORT

SERVER STUB

AMI

SERVER

AMU

CATALOG


call




bind clients and servers together

before RPC can take place.


CLIENT



generator• Query

processing• Code

Generation

TRANSPORT TRANSPORT

SERVER STUB

AMI

SERVER

AMU

CATALOG


call




• Demarshalls the parameters and calls the desired server routine using the regular procedure call mechanism.

• Marshalls the return values into a message.


CLIENT



generator• Query

processing• Code

Generation

TRANSPORT TRANSPORT

SERVER STUB

AMI

SERVER

AMU

CATALOG


call




• Relational user can access non relational model of DB (remotely)

• Using the transport mechanism and corresponding relational schema from the catalog

• The user can access the DB on another node.

Extended RPC Model• RPC provide stub generators for(transport

protocols - data representation - semantics and type systems)

• Extended RPC model support the following cases:First: Local procedure call Relational user can access relational DB which is

locally available Relational user can access network, hierarchical or

other nonrelatinal model of DB.Second: Remote procedure call Relational user can access relational DB on

another node (remotely). Relational user can access nonrelational model of

DB (remotely).

Catalog

The Structure of The Basic Elements of the Model

Non Relational Schema User Information

View Generator

Relational Schema (View) Integrity Constraints

Rule BaseData Base

View Generator

Catalog


View Generator

Non Relational Schema User Information

View Generator

Relational Schema (View) Integrity Constraints

Rule BaseData Base

•Extracts logical information from the given non relational schema and through user-system dialogue at view definition time generates relational schema.•Translated schema is stored in the catalog as relational schema.


• UFI module enabling easy interaction with the resources to the end users.

• UFI module enables processing of user's ad-hoc queries.• Generate relational view over existing relational and non

relational databases.• communicate with the catalog for searching or modifying its

contents.• process ad-hoc queries related on databases resident on one

or more systems.• The UFI will communicate with the user via five types of

screens created by the resident systems : predefined screens for generating relational views over

nonrelational databases, screens for communication with the catalog, predefined screen for all queries, screens for automatic generation of reports, screens defined interactively by the users.

(UFI) User Friendly Interface


(UFI) User Friendly Interface

• UFI transfers user's queries to the lexical analyzer and parser.

• Realize a special SQL parser .• Using high probability.• Syntax error correction activity depends on : The context in which error has occurred, Our knowledge for appropriate recovery action. In this way, we have balanced the efficient query

execution flow with the level of fault tolerant in the process of query parsing.


Query Standardization

View Substitution

Simplification

Amelioration

Evaluation

Selection of Access Plan

Generator of Code

Catalog

Query against View relations (Parse Tree) View relations definition from catalog

The Client Stub - Optimal Access plan generation



View Substitution

Simplification

Amelioration

Evaluation


Generator of Code

Catalog

Query against View relations (Parse Tree) View relations definition from catalog• Using SQL to build prototype

system.• The goal is the construction of a

standardized starting point for query optimization.




View Substitution

Simplification

Amelioration

Evaluation


Generator of Code

Catalog


• Eliminate the redundancy.




View Substitution

Simplification

Amelioration

Evaluation


Generator of Code

Catalog


• construct improve expressions with respect to evaluation performance.




View Substitution

Simplification

Amelioration

Evaluation


Generator of Code

Catalog


• map the transformed query into alternative sequences of elementary operations for which a good implementation and its associated cost are known.




View Substitution

Simplification

Amelioration

Evaluation


Generator of Code

Catalog


• Compute the cost for each access plan, will choose the cheapest one.




View Substitution

Simplification

Amelioration

Evaluation


Generator of Code

Catalog


Generate the code of the access module.




View Substitution

Simplification

Amelioration

Evaluation


Generator of Code

Catalog



• All modules must communicate with the catalog to perform its functions.

• Particular integrity constraints will enable the existing relational view optimization facilities to be used for compiling non relational database.


Server Stub - AMI and AMU

• AMI (Access Method Interface) receive calls from the client stub

• The code generation module in the client stub generates a code which contains calls to the AMI routines.

• The server stub receives the AMI routine name and arguments into network's format.

• The AMU are access method utilities resident on the server system.


The Structure of The Catalog

• The catalog is organized as a knowledge base .

• The knowledge base contains two parts: database - rule base .

• All user requests will be interpreted by the system in accordance with information stored in catalog.

• where and how The catalog should be stored?

Fault-Tolerant Aspects and Recovery

Client 1

Client n

Server 1

Server m

Access Plan 1

Access Plan n

Access Plan 1

Access Plan k


Client 1

Client n

Server 1

Server m

Access Plan 1

Access Plan n

Access Plan 1

Access Plan k

To improve reliability allow the existence and execution

of several access plans


Client 1

Client n

Server 1

Server m

Access Plan 1

Access Plan n

Access Plan 1

Access Plan k

• The client will send messages to multiple servers in the network.

• Choose one of other access plans. The choice can be performed in different ways.

Conclusion• Development of the extended client

server model.• Development of knowledge-based

protocols for user error correction through the query processing.

• Provide an expert subsystem for view definition.

• Development of the catalog structure as relational database and knowledge base.

• Develop fault tolerant model to provide high degree of fault tolerance and robustness of the system.

• Provide better database model and structure transparency.

RELATIONAL FAULT TOLERANT INTERFACE TO HETEROGENEOUS DISTRIBUTED DATABASES Prof. Osama Abulnaja...

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