Summary

Keeping mission-critical systems up and running, including quickly recovering from failures, is one of the most important investment protection measures to be taken. Keeping a system available 24 hours a day, 7 days a week, is a task that requires investments in three areas: people and processes, technology and infrastructure solutions, and support.

Users consider the application an availability of a service. From the more technical IT perspective, availability is the functioning of all the components in the entire mySAP.com application stack, including the environment, the computing hardware and OS, the database, the business applications and the Internet middleware. All of these functions or levels need to be managed from an availability perspective.

This chapter focused on a few of the hardware technology solutions available. Yet, as the system environment becomes larger, with more software applications being added, implementing high-availability solutions becomes more complex. Thus adopting an administration philosophy plays a big role in keeping HA systems actually available.

A few of the important points to consider in high-availability environments for mySAP.com environments are summarized here:

• The definition of system availability from hardware vendors typically only includes the hardware, the operating system, and the clustering software. The database and application are not usually considered in the standard 99.xx% availability ratings.

• The investment in an HA solution should be proportional to the cost of system downtime to the business.

• The backup and restore solution and processes are the most important for maintaining high availability, especially in case of a disaster. Consider a zero downtime backup solution to minimize the backup and restore impact.

• Once the basic recovery processes are in place, then investments in HA failover solutions can be made. There are failover solutions integrated with SAP in Microsoft Windows and Unix environments, with the Unix clustering solutions being the most flexible.

• Standby or recovery database servers can be effectively used for recovery from disasters, from logical errors, and for making decoupled backups.

• To attain even higher levels of SAP application availability, mirroring the SAP single point of failure (the Enqueue Server and Enqueue Table) can be implemented.