Real Application Cluster vs Replication

Oracle Real Application Cluster (RAC)
Real Application Cluster (RAC) is 2 servers or more, each other work together to handle 1 data.
2 Oracle Database Instances with one external data shared storage. So 2 Database Servers is not stand-alone and very different from the Replication.

If the problem occurs in a 1 server, the other server will take over automatically without intervention from the Administrator / Oracle DBA.

RAC aimed for High Availability and High Performance.

Replication
Replication is 2 servers , the 1 is active server and other is standby server (works only receive data replication). So do not work together.

If the problem occurs in the Main Server , it must be taken over /switch to standby server manually, even also need to change ORATNS.ORA on each client PC.

Replication aimed for High Availability and not for High Performance because it only take advantage of performance of the main server.

Oracel to_date function

The Oracle to_date function is used to change a test string (or variable) into an internal date format. The to_date function is usually used in SQL when storing into the database.

Insert into mytab (date_col) values to_date(string,format);

Examples of the to_date function might include:

• to_date('10-12-06','MM-DD-YY')
• to_date('jan 2007','MON YYYY')
• to_date('2007/05/31','YYYY/MM/DD')
• to_date('12-31-2007 12:15','MM-DD-YYYY HH:MI')
• to_date('2006,091,00:00:00' , 'YYYY,DDD,HH24:MI:SS')
• to_date('15-may-2006 06:00:01','dd-mon-yyyy hh24:mi:ss')
• to_date('022002','mmyyyy')
• to_date('12319999','MMDDYYYY')
• to_date(substr( collection_started,1,12),'DD-MON-YY HH24')
• to_date('2004/10/14 21', 'yyyy/mm/dd hh24')
• TO_DATE(First_Load_Time, 'yyyy-mm-dd/hh24:mi:ss'))*24*60)