Database Resource

To draw a presedence graph, you first draw three circles, one for each transaction. Next, you go through the schedule, drawing a line from Transaction A to Transaction B whenever;

B reads an attribute which A has written to at a previous time
B write an attribute which A has written to at a previous time
B writes an attribute which A has read from at a previous time

The connection from Transaction 2 to 1 involving B, and from 3 to 1 involving B do not fall into any of these three categories.

To draw a presedence graph, you first draw three circles, one for each transaction. Next, you go through the schedule, drawing a line from Transaction A to Transaction B whenever;

B reads an attribute which A has written to at a previous time
B write an attribute which A has written to at a previous time
B writes an attribute which A has read from at a previous time

The graph shown has something missing.

To draw a presedence graph, you first draw three circles, one for each transaction. Next, you go through the schedule, drawing a line from Transaction A to Transaction B whenever;

B reads an attribute which A has written to at a previous time
B write an attribute which A has written to at a previous time
B writes an attribute which A has read from at a previous time

All the connections in this graph point the wrong way...

To draw a presedence graph, you first draw three circles, one for each transaction. Next, you go through the schedule, drawing a line from Transaction A to Transaction B whenever;

B reads an attribute which A has written to at a previous time
B write an attribute which A has written to at a previous time
B writes an attribute which A has read from at a previous time

The connection from Transaction 2 to 1 involving B, and from 3 to 1 involving B do not fall into any of these three categories. In addition, the remaining connections in this graph involve the correct attributes and transactions but point the wrong way...

To draw a presedence graph, you first draw three circles, one for each transaction. Next, you go through the schedule, drawing a line from Transaction A to Transaction B whenever;