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

alanced across all members. With the new SYSIBM.IPLIST table, a DB2 for z/OS application
requester can define a specific member or a subset of members in a group to route requests.
At the server, location alias names do not need to be defined to allow these applications to
access the DB2 server with the alternate location names. Aliases are only needed for
member subsetting when the application requester is non-DB2 for z/OS (like DB2 Connect).
The location DB2PLEX might represent three DB2 subsystems in a group: DB2A, DB2B, and
DB2C. As in previous versions, the location DB2PLEX is set up to use the group domain
name to route requests to all available members. If a DBA wants to provide member routing to
DB2A and DB2B but not to DB2C, a location name DB2PLEXA is defined in
SYSIBM.LOCATIONS and a row is inserted for DB2A and DB2B in the SYSIBM.IPLIST table
with their member domain name. If an application wants to route requests to either DB2A or
DB2B, it connects using location DB2PLEXA. When an application wants to route requests to
the least loaded member, it connects using location DB2PLEX.
With this new service, applications can now route requests using a name different than the
group location name. If the application contains SQL statements that qualify object names
with a name other than the group location name, a location alias needs to be defined. In the
above example, DB2A and DB2B need to define location alias DB2PLEXA using the Change
Log Inventory utility. When an application connects to DB2PLEXA and issues a
SELECT * FROM DB2PLEXA.COLLECTION.TABLE;
the DB2 member recognizes the fully qualified object as a local object.
7.1.4 DRDA allows larger query blocks
The DRDA architecture has been enhanced to allow query blocks up to 10 MB.
Description
A query block is a group of rows that fits into a (query) block and is sent as a single network
message. The default query block size used by DB2 in Version 7 is 32 KB. The number of
rows that DB2 puts into a query block depends on the row length, as well as the OPTIMIZE
FOR n ROWS clause. Blocking is used by both DB2 Private Protocol and DRDA. When
blocking is not used, DB2 will send a single row across the network.
To support the larger network bandwidths and customer requirements to control the amount
of data returned on each network request, the DRDA architecture has been enhanced to
allow query blocks up to 10 MB. This way, a DB2 for z/OS V8 requester can ask for a query
block size of up to 10 MB from a DB2 for z/OS V8 server. This allows the requester to better
manage and control the size of blocks returned from DB2.
DB2 Connect V8 and DB2 V8 clients can specify a query block size of up to 65,535 in size but
only the DB2 for z/OS V8 DDF server will support this. Thus, one will notice that the number
of network exchanges between the workstation and DB2 for z/OS V8 server is about half that
when accessing the DB2 for z/OS V7 server. DB2 V7 can only support a query block size up
to 32,767.
Performance
Performance measurement description
In this measurement we used:
► DB2 for z/OS, V7 and V8
► z/OS Release 1.4
► z900
► DB2 Connect EE, Client V8 on 1.3 GHz P690 with AIX
284 DB2 UDB for z/OS Version 8 Performance Topics