Chapter 12. Scalability, reliability, and availability architectures 293
12.3.2  Multiple LPAR sysplex: z/OS
The z/OS operating system has a high availability architecture that is built into it. A z/OS 
Parallel Sysplex is a tightly coupled cluster of independent z/OS systems that connect 
through an Internet Protocol network. A cluster is 2 - 32 independent systems that are locally 
or geographically dispersed. Communication between the z/OS systems in the sysplex is 
handled through the cross-system Coupling Facility (XCF). A z/OS Parallel Sysplex 
implementation provides the highest level of high availability in the industry. 
Figure 12-6 illustrates a Content Manager OnDemand implementation of a two-system highly 
available z/OS sysplex system.
Figure 12-6   Scalability: Parallel Sysplex/multiple LPARs (z/OS)
Figure 12-6 illustrates an example of a two-system Content Manager OnDemand Parallel 
Sysplex implementation. z/OS system A contains a library server and an object server. The 
library server and object server can be either combined in a single executable file (most 
common z/OS implementation) or separated into two executable files, in which case they are 
installed in separate LPARs. z/OS system B shows a multiple LPAR system with a combined 
library/object server that is installed in each of the LPARs.
Both of these systems (all LPARs and all instances of the Content Manager OnDemand 
server) access a single set of Content Manager OnDemand database tables through DB2 
data sharing. They also access a single OAM archive system through an OAMplex. Not 
shown in the figure is the access to a single Job Entry Subsystem (JES) spool and a shared 
file system (which consists of a set of hierarchical file systems (HFS) or z/OS file systems 
(zFS). The term “single” is used to imply that the same set of data is available to all systems 
concurrently. Each of these single systems consists of highly redundant components and 
therefore do not represent a SPOF .
Other
z/OS LPARs
z/OS A z/OS B
LS
OAMPlex
Sysplex Distributor Hot Backup
z/OS B
Sysplex Distributor (SD) WLM*
z/OS A
OS
XCF
LS DB
OAM DB
Shared Data
CMOD Client
LS
OAMPlex
OS
DB2 (Data Sharing) DB2 (Data Sharing)
This could be one LPAR 
Or each component could 
be in an LPAR