7.1 1. While users were updating the TAL Distributors database, one of the trans

Question

7.1

1. While users were updating the TAL Distributors database, one of the transactions was interrupted. You need to explain to management what steps the DBMS will take to correct the database. Using the sample log shown in Figure 7-11 (above), list and describe the updates that the DBMS will roll back if transaction 2 is interrupted at 8:10.

Transaction ID Time Action Record Updated Before Image After Image 8:00 Start 8:01 Start 8:02 Insert 8:03 Start 8:04 Update Item (FD11) 8:05 Insert 8:06 Commit 8:07 Start 8:08 Insert 8:09 Insert 8:10 Commit 8:11 Update Item (FD11) 8:12 Update Item (TW35) 8:13 Delete 8:14 Update Customer (260) 8:15 Commit 8:16 Update Rep (30) 8:17 Commit Orders (51630) (new values) (old values) (new values) (new values) OrderLine (51630, FD11) 4 (new values) (new values) Customer (510 OrderLine (51630, TW35) (old values) (old values) (old values) (old values) (new values) (new values) 4 Item (AH74) (new values) 4 (old values) (new values)

Explanation / Answer

updates that the DBMS will roll back if transaction 2 is interrupted at 8:10 are:

Insert Customer (510)

Insert OrderLine (51630, TW35)

Description:
When transaction 2 is interrupted at 8:10, DBMS will rollback the following transactions which are not yet committed into the database.
1.the Insert Customer (510)
2.Insert OrderLine (51630, TW35)

All the transactions which happened before the above transactions (Insert Orders (51630), Update Item (FD11), Insert OrderLine (51630, FD11)) are committed into the database by the Commit statement executed successfully at 8:06

Insert Customer (510):
means, to insert a new record into Customer table with primary key value 510

Insert OrderLine (51630, TW35):
means, to insert a new record into OrderLine table with primary key value 51630, TW35

Steps the DBMS will take to correct the database, if transaction 2 is interrupted at 8:10 :

Insert Customer (510)

Insert OrderLine (51630, TW35)

Commit;

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