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2.7 Database server
Another component that is critical for the availability of an SAP system is the database server.
If the database server cannot be reached, the entire SAP system is unavailable.
Consequently, you must pay special attention to keeping the database up and running.
2.7.1 Non-data sharing environment
2.7.2 Data sharing
In a non-data-sharing environment, the database server is a SPOF and must be stopped
whenever there is a need to apply maintenance or upgrade the database or the z/OS. As a
consequence, planned outages are unavoidable, but they can be scheduled at a more
convenient time.
A data sharing configuration eliminates the database server as a SPOF and provides nearly
continuous availability. In contrast to a non-data sharing setup, planned outages can be
avoided by using a DB2 connection failover. If planned maintenance occurs, the workload is
moved from the affected DB2 member to an available one within the data sharing group. DB2
connection failover is also used for unplanned outages to switch the workload. In both
scenarios, the SAP system remains available to the users.
To guarantee business continuity, you must install the DB2 database in data sharing mode.
You must also run the SAP Central Services on z/OS.
For the failover scenarios, use separate virtual host names for each service. Figure 2-6 shows
four SAP NetWeaver ASs connected to three DB2 data sharing members. The black lines
visualize the primary connections. These connections can be redirected without disruption to
other DB2 members if failure occurs or to apply online maintenance for specific DB2
members.
SAP NetWeaver
AS
DB2 data sharing
group
DB2
Figure 2-6 DB2 data sharing
SAP NetWeaver
AS
20 Running SAP Solutions with IBM DB2 10 for z/OS on the IBM zEnterprise System
DB2
SAP NetWeaver
AS
SAP NetWeaver
AS
DB2