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The ACID Model

The ACID Model
http://databases.about.com/od/specificproducts/a/acid.htm

The ACID model is one of the oldest and most important concepts of database theory. It sets forward four goals that every database management system must strive to achieve: atomicity, consistency, isolation and durability. No database that fails to meet any of these four goals can be considered reliable.

Let’s take a moment to examine each one of these characteristics in detail:

* Atomicity states that database modifications must follow an “all or nothing” rule. Each transaction is said to be “atomic.” If one part of the transaction fails, the entire transaction fails. It is critical that the database management system maintain the atomic nature of transactions in spite of any DBMS, operating system or hardware failure.
* Consistency states that only valid data will be written to the database.
If, for some reason, a transaction is executed that violates the database’s consistency rules, the entire transaction will be rolled back and the database will be restored to a state consistent with those rules. On the other hand, if a transaction successfully executes, it will take the database from one state that is consistent with the rules to another state that is also consistent with the rules.
* Isolation requires that multiple transactions occurring at the same time not impact each other’s execution. For example, if Joe issues a transaction against a database at the same time that Mary issues a different transaction, both transactions should operate on the database in an isolated manner. The database should either perform Joe’s entire transaction before executing Mary’s or vice-versa. This prevents Joe’s transaction from reading intermediate data produced as a side effect of part of Mary’s transaction that will not eventually be committed to the database. Note that the isolation property does not ensure which transaction will execute first, merely that they will not interfere with each other.
* Durability ensures that any transaction committed to the database will not be lost. Durability is ensured through the use of database backups and transaction logs that facilitate the restoration of committed transactions in spite of any subsequent software or hardware failures.

Take a few minutes to review these characteristics and commit them to memory. If you spend any significant portion of your career working with databases, you’ll see them again and again. They provide the basic building blocks of any database transaction model.

不扣纽扣的女孩posted by kingchrisg at 11:34 AM 0 comments不扣纽扣的女孩

不扣纽扣的女孩

Europe for Spring Break

3/11/06: Ready for takeoff!


3/12/06: "... and the next thing I knew was we were in Paris, eating bagettes, waiting for the train!"


3/13/06: Nice Bright Apartment


Where the bright light comes from - they are right on the beach!


Apartment Stairway


Dunkerque


The only person I know who has a footwear industry scholarship


The school




Sophie, Zac and Emma at Dinner beneath Carnival costumes


3/14/06: Leaving Emma & Sophie's Apartment for the Belgium Bus


A typical afternoon snack in Brussels!


3/15/06: The Dom in Cologne


In the Dom spire looking up -


3/16/06: On the way back to Dunkerque by train -


What better dessert than a crepe suzette on your last night in France!


3/17/06: Returned on St. Patty's Day where even the French are celebrating -

Tuesday, April 04, 2006

Six Career Secrets You Won't Learn in School

Six Career Secrets You Won't Learn in School

By Alexandra Levit, author of "They Don't Teach Corporate in College: A Twenty-Something's Guide to the Business World"

Since they don't teach corporate in college, here are six tips to help you win at the business world's game:

1. Develop (yourself as) a marketable corporate person:

2. Establish profitable relationships:

3. Master transferable skills like goal setting, effective communication and time management:

4. Stay motivated despite trying circumstances:

5. Get people to cooperate:

6. Be proactive about your career growth:

Alexandra Levit worked for a Fortune 500 software company and an international public relations firm before starting Inspiration @Work, a career consulting and corporate training business. She's the author of "They Don't Teach Corporate in College: A Twenty-Something's Guide to the Business World" (Career Press 2004). Web site: www.corporateincollege.com.

Monday, April 03, 2006

Seven Ways to Start Your New Job Right

3/29/06Seven Ways to Start Your New Job Right by Jim Citrin

Seven Ways to Start Your New Job Right

-- here are seven steps to follow:

1. Prepare Yourself During the "Countdown Period"
2. Align Expectations
3. Shape Your Management Team
4. Craft Your Strategic Agenda
5. Assess and Start Transforming the Culture
6. Establish a Productive Working Relationship with Your Board or Boss
7. Communicate!

Thursday, March 09, 2006

Off to France

Pat and I are taking Zac and Christopher to France to visit Emma on her Junior year abroad in Dunkerque.Both the guys have Spring break on the same week and are keen on getting out of their respective college towns.

We have tentative plans to:
swim in the English Channel,
stay in a beachside pension while the guys stay at Emma's,
cross the channel by ferry to see the cliffs of Dover,
go to Brussels,
go to Cologne,
go down the coast to visit more northern France beaches,
go to Lille, etc.

Dunkerque was only found in 1 of 5 France guidebooks I researched and most relevant paragraph, roughly paraphrased, went something like this -
"Dunkerque, an industrial port, was completely flattened in WW2 and was then built back up quickly with really ugly 1950's style buildings.If you find yourself there in the evening by mistake, plan to spend the night to rest up, then move on early the next day"
- not very encouraging.

Some highlights -
the Flanders area is the one part of France where more beer than wine is consumed.
Dunkerque is known for several excellent Carnival celebrations, both pre and during Lent, that Emma tells us are a good time.

I'll write more when we return and hopefully have some good pictures to share.