Performance Enhancement of Read-only Transactions Using Speculative Locking Protocol T. Ragunathan and Dr. P. K. Reddy

Problems in Processing Read-only Transactions (ROTs) Correctness ( Serializability criteria)

Data Currency ( Transactions receive old values)

Performance ( Throughput)

The performance of 2PL degrades with data contention.

Example:

Snapshot Isolation(SI)-based protocols violate serializability criteria and provide less data currency to ROTs.

Example:

Proposed Speculation based approach (SLR) ROTs are processed with speculation.

Whenever a UT produces after-image, ROTs access both before- and after-images and start speculative executions.

Parameters Values

# of objects in the database 1000

Time to carry out CPU and I/O requests 5ms and 10ms

Size of the largest and smallest ROT 20 and 15 objects

Size of the largest and smallest UT 15 and 5 objects

Simulation Parameters and Values.

Simulation Results

Throughput performance is Improved significantly over SI and 2PL.

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MPL

Th

rou

gh

pu

t

2PL

SIFC

SLR

# UTs 30%- # RUs = 8

Data currency of ROTs improved significantly over SI.

# UTs 30 % , 8 RUs

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MPL

Cu

rren

cy

Gain

SLR

SIFC

Requires manageable extra processing resources ( 1.4 times of memory is required).

Conclusions Proposed speculation based approach improves the performance of ROTs significantly over other protocols.

It does not violate serializability criteria.

It processes ROTs without data currency problems.

The experimental results show that it requires manageable ( 1.4t imes) extra processing resources.

Center for Data EngineeringInternational Institute of Information Technology, Hyderabad

http://cde.iiit.ac.in

Example:

Asynchronous Speculative Locking Protocol for improving the performance of Read-only Transactions - T. Ragunathan and Dr. P. K. Reddy

The performance of 2PL degrades with data contention.

Snapshot Isolation(SI)-based protocols violate serializability criteria and provide less data currency to ROTs.

Synchronous speculation based approach (SLR)

Improves performance and data currency. ROTs wait for lock conversion ( EW-lock in to SPW-lock)

Parameters Values

# of objects in the database 1000

Time to carry out CPU and I/O requests 5ms and 10ms

Size of the largest and smallest ROT 20 and 15 objects

Size of the largest and smallest UT 15 and 5 objects

Requires manageable extra processing resources ( 1.5 times of memory is required).

Conclusions

Proposed asynchronous speculation based approach improves the performance of ROTs significantly over other protocols.

It does not violate serializability criteria.

The experimental results show that it requires manageable ( 1.5 times) extra processing resources.

Center for Data EngineeringInternational Institute of Information Technology, Hyderabad

http://cde.iiit.ac.in

Example:

Proposed Asynchronous speculative locking protocol (ASLR) ROTs do not wait for lock conversion and can start executions with the available before-images.

However ROTs perform speculative executions whenever UTs produce after-images. When an ROT commits, it commits with the appropriate speculative execution.

Performance is better than SLR.

Simulation Parameters and Values.

Simulation Results

# RUs = 8, % UTs = 30, MPL = 20

69.008

23.714

6.0581.069

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% o

f Tra

nsac

tions 1 Execution

2 Executions4 Executions8 Executions

Throughput performance is Improved significantly over SI, 2PL and SLR.

Example:

0

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80

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MPL

Th

rou

ghp

ut

2PL

SIFC

ASLR

SLR

# UTs = 30% , # RUs = 8