Wed, Oct 27, 1999
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- Introduction to Module 3

- Recall ACID Properties (from Module 1)

- Banks and Salaries Example
	- Two people
	- Two transactions

- Introduction to Schedules
	- A time-ordered sequence of important actions taken
	by one or more transactions
	- restrict ourselves to only reads and writes (why?)

- A Serial Schedule
	- is one which consists of the actions of one transaction
	followed by the actions of another
	- no mixings

- A Serializable Schedule
	- is one which performs "equivalent" to "some" serial schedule
	- notice the word "some"

- A simple combinatorial problem

- Notation for Transaction Operations 
	- can safely omit operations other than read, write etc. why?
	- E.g. r_1(A), w_2(B)

- Conflicts between reads and writes

- In general, there is no conflict, unless
	- both transactions involve the same element AND
	- one of them is a write

- Conflict-Equivalency
	- Notion that one schedule can be "changed" into another
	by a swapping of neighboring actions