Concurrency control manages simultaneous database operations to prevent interference. It enforces isolation through techniques like locking to resolve conflicts. The main goals are preserving consistency, resolving read-write and write-write conflicts, and maintaining integrity despite lost updates or inconsistent data. Approaches include lock-based protocols, timestamp-based protocols, and validation-based protocols.
Distributed database system is collection of loosely coupled sites that are independeant of each other.
Distributed transaction model
Concurrency control
2 phase commit protocol
Distributed database system is collection of loosely coupled sites that are independeant of each other.
Distributed transaction model
Concurrency control
2 phase commit protocol
Powerpoint Presentaion on Concurrency Control Protocols,
is part of Btech 3rd year DBMS syllabus.
This slide is part of assignment provided during session 2018-2019
Multi version concurrency control techniques
This approach maintains a number of versions of a data item and allocates the right version to a read operation of a transaction. Thus unlike other mechanisms a read operation in this mechanism is never rejected.
Powerpoint Presentaion on Concurrency Control Protocols,
is part of Btech 3rd year DBMS syllabus.
This slide is part of assignment provided during session 2018-2019
Multi version concurrency control techniques
This approach maintains a number of versions of a data item and allocates the right version to a read operation of a transaction. Thus unlike other mechanisms a read operation in this mechanism is never rejected.
Operator Overloading and Scope of VariableMOHIT DADU
This slide is completely based on the Operator Overloading and the Scope of Variable. The example given to explain are based on C/C++ programming language.
Concurrency Control Techniques: Concurrency Control, Locking Techniques for Concurrency
Control, Time Stamping Protocols for Concurrency Control, Validation Based Protocol, Multiple
Granularity, Multi Version Schemes, Recovery with Concurrent Transaction,
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
2. CONCURRENCY: In computer science,
concurrency is a property of systems in which
several computations are executing simultaneously,
and potentially interacting with each other.
• Concurrency control is the process of managing
simultaneous operations on the database without
having them interfere with one another.
• Concurrent access is relatively easy if all users are
only reading data, as there is no way that they can
interfere with one another.
3. Purpose of Concurrency Control
• To enforce Isolation (through mutual exclusion)
among conflicting transactions.
• To preserve database consistency through consistency
preserving execution of transactions.
• To resolve read-write and write-write conflicts.
In concurrent execution environment if T1
conflicts with T2 over a data item A, then the existing
concurrency control decides if T1 or T2 should get the
A and if the other transaction is rolled-back or waits.
4. Simultaneous execution of transactions over a shared
database can create several data integrity and
consistency problems:
• Lost Updates.
• Uncommitted Data.
• Inconsistent retrievals.
Why we need Concurrency
Control
5. When we need Concurrency Control
1. The amount of data is sufficiently great that at any
given time only fraction of the data can be in primary
memory & rest should be swapped from secondary
memory as needed.
2. Even if the entire database can be present in primary
memory, there may be multiple processes.
9. This is the most commonly used concurrency protocol.
This protocol uses either System Time or Logical
Counter as a timestamp.
Lock-based protocols manage the order between the
conflicting pairs among transactions at the time of
execution, whereas timestamp-based protocols start
working as soon as a transaction is created.
10. Every transaction has a timestamp associated with it,
and the ordering is determined by the age of the
transaction.
Every data item is given the latest read and write-
timestamp. This lets the system know when the last
‘read and write’ operation was performed on the data
item.
Timestamp based algorithm uses timestamp to
serialize the execution of concurrent transactions.
11. This is the responsibility of the protocol system that
the conflicting pair of tasks should be executed
according to the timestamp values of the transactions.
•The timestamp of transaction Ti is denoted as TS(Ti).
•Read time-stamp of data-item X is denoted by R-
timestamp(X).
•Write time-stamp of data-item X is denoted by W-
timestamp(X).
12. 1. Transaction Ti issues a write_item(X) operation:
• If TS(Ti) < R-timestamp(X), then the value of X that Ti is
producing was needed previously, and the system assumed that
that value would never be produced. Hence, the write
operation is rejected, and Ti is rolled back.
• If TS(Ti) < W-timestamp(X), then Ti is attempting to write
an obsolete value of X. Hence, this write operation is rejected,
and Ti is rolled back.
• Otherwise, the write operation is executed, and W-
timestamp(X) is set to TS(Ti).
13. • If TS(Ti) W-timestamp(X), then Ti needs to read
a value of X that was already overwritten. Hence, the
read operation is rejected, and Ti is rolled back.
• If TS(Ti) W-timestamp(X), then the read
operation is executed, and R-timestamp(X) is set to
the maximum of R-timestamp(X) and TS(Ti).
2. Transaction T issues a read_item(X) operation:
14. Advantages:
–Schedules are serializable (like 2PL protocols)
–No waiting for transaction, thus, no deadlocks!
•Disadvantages:
-- Starvation is possible (if the same transaction is
continually aborted and restarted)
15. Thomas’s Write Rule:
• If read_TS(X) > TS(Ti) then abort and roll-back
Ti and reject the operation.
• If write_TS(X) > TS(Ti), then just ignore the
write operation and continue execution. This is
because the most recent writes counts in case of
two consecutive writes.
• If the conditions given in 1 and 2 above do not
occur, then execute write_item(X) of Ti and set
write_TS(X) to TS(Ti).
17. Execution of transaction Ti is done in three phases.
1. Read and execution phase: Transaction Ti writes only to
temporary local variables
2. Validation phase: Transaction Ti performs a ``validation test''
to determine if local variables can be written without violating
serializability.
3. Write phase: If Ti is validated, the updates are applied to the
database; otherwise, Ti is rolled back.
Also called as optimistic concurrency control since transaction
executes fully in the hope that all will go well during validation
18. Each transaction Ti has 3 timestamps
Start(Ti) : the time when Ti started its execution
Validation(Ti): the time when Ti entered its validation phase
Finish(Ti) : the time when Ti finished its write phase
Serializability order is determined by timestamp given at
validation time, to increase concurrency. Thus TS(Ti) is given
the value of Validation(Ti).
This protocol is useful and gives greater degree of concurrency
if probability of conflicts is low. That is because the
serializability order is not pre-decided and relatively less
transactions will have to be rolled back.
19. If for all Ti with TS (Ti) < TS (Tj) either one of the
following condition holds:
finish(Ti) < start(Tj)
start(Tj) < finish(Ti) < validation(Tj) and the set of
data items written by Ti does not intersect with the
set of data items read by Tj.
then validation succeeds and Tj can be committed.
Otherwise, validation fails and Tj is aborted.
20. Justification: Either first condition is satisfied, and
there is no overlapped execution, or second condition
is satisfied and
1. the writes of Tj do not affect reads of Ti since they
occur after Ti
has finished its reads.
2. the writes of Ti do not affect reads of Tj since Tj does
not read
any item written by Ti.
21. Example of schedule produced using validation
T14 T15
read(B)
read(B)
B:- B-50
read(A)
A:- A+50
read(A)
(validate)
display (A+B)
(validate)
write (B)
write (A)