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

You can keep the DBRMs in EBCDIC format if you use NEWFUN(NO), but you cannot use
any new functions.
2.6.4 SUBSTRING function
Once you go into ENFM and beyond, you can use the new V8 SUBSTRING built-in function,
which is character-based. The old V7 SUBSTR function continues to be byte-based. DB2 V8,
with APAR PQ88784, introduces a number of new “character-based” functions rather than the
older “byte-based” functions. Some code pages have special characters that can now result in
more than one byte in Unicode, so you may get different results using SUBSTRING. Make
sure you use the right substring function to get the correct results.
Several new functions are added and several existing functions are enhanced to allow the
processing of character data in more of a "character-based" than "byte-based" manner. The
new functions are:
► CHARACTER_LENGTH
► POSITION
► SUBSTRING
The changed functions are:
► CHAR
► CLOB
► DBCLOB
► GRAPHIC
► INSERT
► LEFT
► LOCATE
► RIGHT
► VARCHAR
► VARGRAPHIC
The new and changed functions allow you to specify the code unit in which the strings should
be processed. That is, CODEUNITS determines how to interpret a character string.
2.7 New installation default values
In this section, we list the changes that have taken place to the default values of several buffer
pool threshold settings in DB2 V8. These new values are the result of system performance
tuning work done by the DB2 Development Performance Department in SVL, and
considerations related to a more general applicability of those values. They are applied to
your system if you are doing a new install of DB2 and select not to specify the values yourself.
If you are migrating to V8, and your parameter values are specified as the old defaults, then
you should consider changing to the new values for improved performance and availability,
particularly CACHEDYN and CHKFREQ.
We also list the new DSNZPARM default values. These are changes to the defaults in the
installation CLIST for DB2 V8 which affect your definitions if you are just letting the panels
assume defaults. If this is the case, and you want to compare performance across V7 and V8
in compatibility mode, you might want to review the new values and set them back to the old
defaults, at least for the initial period.
24 DB2 UDB for z/OS Version 8 Performance Topics