DB2 UDB for z/OS Version 8 Performance Topics - IBM Redbooks

7.1 DDF enhancements
A requester database alias, a server location alias and member routing in a TCP/IP network
are provided in DDF.
7.1.1 Requester database alias
During this discussion, in which we want to differentiate between DB2 for z/OS and DB2 for
Linux, UNIX, and Windows, we call the latter DB2 for Multiplatforms.
A DB2 for Multiplatforms database is known in the network by its database name. This
database name is used by applications to connect to an instance of a for Multiplatforms
database. A DB2 for z/OS requester uses a location name to connect to an instance of a DB2
for Multiplatforms database. A location name maps to a DB2 for Multiplatforms database
name. When a DB2 for Multiplatforms database is deployed to a large number of servers, in
some cases in the thousands, the database is commonly deployed with the same name in
different locations.
The current Communications Database catalog tables require a one to one mapping with a
location and a network address. A location can only be defined to one network address. To
allow a z/OS requester to access multiple DB2 for Multiplatforms databases with the same
database name, a new column is added to SYSIBM.LOCATIONS table called DBALIAS. This
column allows a database administrator to specify multiple locations for a DB2 for
Multiplatforms database deployed on multiple locations. A z/OS application would then
specify a location name to access an instance of a DB2 for Multiplatforms database and the
SYSIBM.LOCATIONS would map the location name to the DB2 for Multiplatforms database
name which is then used to connect to the DB2 for Multiplatforms database.
7.1.2 Server location alias
A DB2 server is known in the network by its location name. This name is used by applications
to identify an instance of a DB2 subsystem or a group of data sharing DB2 subsystems.
When two or more DB2 subsystems are migrated to a single data sharing group, multiple
locations must be consolidated into a single location. When the locations are consolidated, all
applications using the old location name need to be changed to access the new data sharing
group location name.
When there is a large number of remote applications deployed across the network, in some
cases in the thousands, it is impossible to effectively change each application simultaneously
to use the new location name. In order to support the migration from multiple locations to a
single location, eight location alias names can be defined for a DB2 subsystem or group of
data sharing DB2 subsystems.
A location alias is another name that a requester can use to access a DB2 subsystem. DB2
accepts requests from applications that identify the DB2 server with its location name or any
of its location alias names. The Change Log Inventory utility allows a user to define up to eight
alias names in addition to the location name. The Print Log Map utility prints any location alias
names defined for the DB2 subsystem.
7.1.3 Member routing in a TCP/IP Network
In a sysplex environment, setting up rows in the new SYSIBM.IPLIST table at a requester in
conjunction with defining location aliases at the server provides the ability for a DBA to
override the default TCP/IP workload balancing. Currently, connections are automatically
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