Category Archives: Internship Notes

Solution

• If database monitors locking process too frequent, leads to inefficiency.

Optimistic Locking – UPDATE, COMMIT

Lock when there is a change or updates

Both users can retrieve the record

When the user updates the record, the database will lock user A to disallow user A to update.

Problems

• User A (value=1000, rcdversion=1)
• User B (value=1000, rcdversion=1) – If update, rcdversion+1
• After the update:User A: rcdversion=1User B: rcdversion=2

Solution

UPDATE <table>

SET …..

rcdversion=rcdversion+1

WHERE primarykey=”…..”

AND rcdversion=original value

Commitment Control

• Maintains integrity of database where each ‘logical’ transaction consist of multiple updates or inserts or deletes. (Receiver and Sender)
• Logical transactions happened, updates three tables.
• If one of them not updates, the transaction is rollback.
  conn.setAutoCommit(true);
  conn.setAutoCommit(false);

• take control
• will update until execute

update statements

…

…

conn.commit();
conn.rollback();

If master file splits, more secure because master file being copied by others is meaningless.

E.g. code tables

• country codes
• currency codes

Standalone and Dependent

• Master file
• Code file
• Transaction file
• Audit log file

• Triggers: Automatic
• Stored Procedures: functions to be called.
• Oracle/PostgreSQL: PL/SQL
• Microsoft SQL Server: Transact/SQL

• Do not display for the first time until field entered.
• AssetMasterBean(Collection) – FaultsBean