IBM Systems Magazine, Mainframe Edition - September/October 2011 - (Page 42)

Tips and Techniques Tactical solutions Small Steps to Big Gain New Function Mode helps save CPU resources By Jeff Berger I n a previous issue, I outlined how you can save CPU resources using Conversion Mode when migrating to DB2* 10 for z/OS*. This article will examine the CPU savings you may achieve when you migrate to New Function Mode and begin to exploit the new functions. Non-key index columns are a new method of enabling index-only access while at the same time minimizing the number of indexes and enforcing key uniqueness. Reducing the number of indexes, IBM has observed a 10- to 30-percent CPU reduction for inserts. Dynamic Statement Literal Replacement is a new method for helping improve the hit ratio in the global dynamic-statement cache, which reduces the CPU time when query statements differ only with respect to the particular literal value. For LOBs, Copy and Recover can use FlashCopy* to create and restore virtual storage access method (VSAM) image copies, thereby saving all of the CPU time associated with copying a DB2 object the old-fashioned way. Measurements have shown FlashCopy technology saves CPU time for objects bigger than 7 MB: the bigger the object, the greater the savings. Before DB2 10, a stored procedure could only return result sets to the intermediate caller. If the stored procedure is in a chain of nested calls, the result sets must be materialized at each intermediate nesting level, Editor’s Note: This is the second in a series on reducing CPU resources or MIPS using DB2 10 for z/OS. The previous installment summarized Conversion Mode. Read it online: www.ibmsystemsmag. com/mainframe/DB2_Conversion_ Mode/35536p1.aspx How to Utilize New Functions Two new functions require universal table spaces and will help with CPU performance: inline large objects (LOBs) and hash access. Now small LOBs can be inlined with the other columns in the row. If a LOB is small enough to be completely inlined, the aux index and LOB table space aren’t used, eliminating a lot of getpages and I/Os, as well as simplifying space management. The smaller the LOBs, the greater the CPU savings—especially when sequential processes are involved. Hash access is a new table-space organization that can save CPU costs when a clustering index isn’t needed. Hash access is applicable when the data doesn’t need to be clustered according to a clustering key, and where the queries involve equal predicates or an IN list predicate. IBM applied a hash access to its IBM Relational Warehouse Workload (IRWW). IRWW is an IBM laboratory transaction workload that uses IMS* as a front end. IBM determined 55 percent of the tables merited conversion to hash access, resulting in a 10-percent CPU savings. 42 S E P TE M B E R /O CTO B E R 2 011

Table of Contents for the Digital Edition of IBM Systems Magazine, Mainframe Edition - September/October 2011

IBM Systems Magazine, Mainframe Edition - September/October 2011
On the Web
Editor’s Desk: Support in the Long Run
Dashboard: Form Meets Function
Data Display: The Cost of a Breach
Insider: Testing Proves Deduplication for Mainframes is Worthwhile
Trends: System z Servers and Tivoli Software Go Beyond Virtualization
Dream Machine: zEnterprise Creates an Ideal Multiarchitecture Infrastructure, Perfect for Cloud
Growth Through Learning: IBM Academic Initiative Expands in Response to Industry Demand
Focus on Storage: The Latest z/OS Release Brings File System Support for OAM
Tips & Techniques: New Function Mode Helps Save CPU Resources
Advertisers’ Index
Stop Run: Students John Noel and Regina Robins win big at Spring SHARE
Reference Point
2012 Mainframe Buyer's Guide
Services Blueprint: IBM Lab Services and Timing

IBM Systems Magazine, Mainframe Edition - September/October 2011