copy of parallel database systems
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Parallel Database Systems
PARALLEL DATABASE PARALLEL DATABASE SYSTEMSSYSTEMS
Under the guidance of :
Mr. Anisur Rahman
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Parallel Database Systems
INTRODUCTIONA parallel database system (PDBS) is a DBMS implemented on a parallel computer which is made of a number of nodes (processors and memories) connected by a fast network within a cabinet.
It strives to exploit modern multiprocessor architectures using software-oriented solutions for data management.
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OBJECTIVEProblems of conventional DBMS
- high disk access time.
- very large databases cant be supportedwithin a single system.
PDBS is the only viable solution for increasing the I/O bandwidth through parallelism & for storing huge databases in a single system.
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ADVANTAGES OF PDBS High Performance – Increased throughput
(inter-query parallelism) & decreased response time (intra-query parallelism).
High Availability – Using data replication.
Extensibility – Linear scaleup and Linear speedup.
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PARALLEL DBMS ARCHITECTURE
Shared Memory Advantages – Simplicity, Load Balancing. Problems – Cost, Limited Extensibility, Low
Availability.
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Shared Disk Advantages – Cost, Extensibility, Load Balancing,
Availability.Problems – Higher Complexity, Potential Coherence
Problems.
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Shared NothingAdvantages – Cost, Extensibility, Availability.Problems – Complex, Addition of new nodes requires
reorganizing the database.
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PARALLEL DBMS TECHNIQUESDATA ALLOCATION – Methods that spread the database across the system’s disks to ensure efficient parallel I/O. Partitioning (Fragmentation) – 3 strategies # Round Robin – i th tuple to partition (i mod n)
for n partitions. # Hashing – Apply hash function to some attribute to give partition no. # Range Partitioning – Distribute tuples based
on value(ranges) of some attribute.
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elUSES OF DATA FRAGMENTATION Maximize system performance.
Minimize response time (through intra-queryparallelism).
Maximize throughput (through inter-queryparallelism).
Problems: Skewed data distributions lead tonon-uniform partitioning & hurt load balancing.
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QUERY PARALLELISM Inter query parallelism – parallel execution of multiple queries generated by concurrent transactions.
Intra query parallelism – Two kinds:#Inter-operator – Executing several operators of
the query tree on several processors in parallel.#Intra-operator – Same operator is executed by
many processors, each one working on a subset of the data.
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PARALLEL ALGORITHMS
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PARALLEL JOIN EXAMPLE
Insert into C Select * from A , B where A.x = B.y ;
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CONCLUSIONThe availability of fast microprocessors &
small inexpensive disks is an ideal platform for parallel database systems.
Employing data partitioning, intra-operator parallelism etc., converting an existing DBMS into a highly parallel one is relatively straightforward.
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