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

z9-109 I/O Overview
I/O Enhancements
– Up to 28 FICON Express/FICON Express2 features
per I/O cage
• 4 channels/feature FICON/FCP
• 1, 2 Gbps auto-negotiated
– Modified Indirect Data Address Word (MIDAW) facility
– Multiple (2) Subchannel sets (MSS)
• Increase to 63.75K Subchannels for Set-0
– Up to 64* x 2.7GB STI’s (21 STIs max for 3 I/O cages)
Storage Area Networks (SANs) enhancements
– N_Port ID Virtualization
– Program Directed re-IPL
– FICON Link Incident Reporting
Networking enhancements
– HiperSockets IPv6
– OSA-Express2 1000BASE-T Ethernet
– OSA-Express2 OSN (OSA for NCP support)
– GARP VLAN management (GRVP) * z9-109 exploits a subset of its designed I/O capability
9109TLLB 1
Figure 4-21 IBM System z9
©2005IBMC ti
The use of MIDAWs reduces the number of frames and sequences flowing across the link,
making the channel more efficient.
Figure 4-22 summarizes the comparisons with and without MIDAW for a partitioned table
space scan. Page fixing is active and the table space is in EF.
The I/O response time is reduced by about 50%, and gets even better increasing the number
of partitions. Channel utilization is largely reduced, and the throughput increases up to 186
MB/sec, close to the FICON link nominal capability of 200 MB/sec in one direction.
Chapter 4. DB2 subsystem performance 203