One of the advanced feature used for HA is failover, wherein a workload is 

transferred from one system to another quickly and automatically in case of 

failure.

MySQL does not support

automatic high availability, instead you have to use 

replication features of MySQL to support high availability. You have to set up a 

master and slaves, and write scripts that will monitor the master to see if it is up 

and running, and as soon as the master gets down one of the slave, it acts like a 

master. 

DB2 UDB has an advanced continuous checkpointing system and a parallel 

recovery capability that allows for extremely fast crash recovery. DB2 UDB 

fail safe can be achieved in number of ways, most frequently used once are:

Log shipping

In log shipping, whole log files are shipped to a standby machine though 

achieve file or user exit program running against primary database. The 

standby database is continuously rolling forward through the log files 

produced by the production machine. Now, as soon as main server gets 

down, the remaining logs are transferred to the standby machine, and the 

standby database rolls forward and the client resumes its services by 

reconnecting to the standby machine.

Suspended I/O

Suspended I/O supports a quick initialization of new database by making a 

split mirror. A split mirror is instantaneous copy of the database that can be 

made by mirroring the disks containing the data, and splitting the mirror when 

a copy is required.

The 

db2inidb

 command initializes the split mirror so that it can be used:

As a clone database

As a standby database

As a backup image

DB2 UDB failover can also be achieved using platform specific software:

High Availability Cluster Multi Processing, Enhanced Scalability, for AIX

Microsoft Cluster Server, for Windows operating systems

Sun Cluster, or VERITAS Cluster Server, for the Solaris Operating 

Environment

Steeleye's Linux based high reliability solution for DB2 UDB

Apart from failover, DB2 UDB uses features like online buffer pools, online 

backup, and loading of data, online table, and index organization for providing 

uninterrupted service.

 Chapter 8. Database administration 

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