Chapter 12. Scalability, reliability, and availability architectures 285
Basically, two redundancy techniques are available:
/SM590000Passive redundancy: This redundancy is achieved by including enough excess capacity in 
the design to accommodate a performance decline, such as two Content Manager 
OnDemand servers (known as ARSSOCKD on z/OS and Multiplatforms) that access the 
same system tables and archive. If one server fails, the other server is available to take on 
the workload.
/SM590000Active redundancy: This redundancy is used to achieve high availability with no 
performance decline. In this case, at least double the required resources are allocated to 
the Content Manager OnDemand system. For example, if the peak workload requires 1.5 
Content Manager OnDemand servers, three Content Manager OnDemand servers are 
configured to work in parallel. If one of the servers fails, the other two servers can take on 
the full workload with no performance degradation.
Systems typically become unavailable because of the lack of one or more of the following 
activities:
/SM590000Change control procedures (a failure to implement the appropriate procedures from 
installation verification through performance testing before you place the system into 
production)
/SM590000Monitoring of production system components (including total system workload, hardware, 
and network issues)
/SM590000Implementing high availability solutions (redundant systems and network connections)
/SM590000A comprehensive backup (and restore) process that is tested on a routine basis
A cost exists to implementing highly available high-performance systems. This cost must be 
weighed against the cost of not implementing such systems.
The following sections provide more information about example system implementations that 
allow high performance, scalability, reliability, and availability.
12.2  Scaling a Content Manager OnDemand system
A Content Manager OnDemand instance can be scaled from a single system image that 
performs all of the required tasks (data loading, library storage, and object storage) to a 
multiple system/multiple LPAR configuration, which offers higher levels of performance and 
availability. When a Content Manager OnDemand instance is distributed among multiple 
systems, these systems might be configured in the following ways:
/SM590000Single technology systems: The Content Manager OnDemand instance consists of 
systems that are of the same architecture. For example, all systems might be AIX 
systems.
/SM590000Multiple technology systems: The Content Manager OnDemand instance might consist of 
systems of different architectures. For example, the library server and an object server 
might be on a z/OS system; two other object servers might be on AIX systems; and 
another object server might be on a Microsoft Windows system.
In both of these scenarios, the configuration results in a single Content Manager OnDemand 
instance view from both the administrative and user perspectives.
With this flexibility and scalability, you can configure Content Manager OnDemand systems 
so that they meet a wide range of both workload and operational requirements.