DB2 bufferpool Pagefixing por Alvaro Salla

1. DB2 V8 Bufferpool Pagefixing For saving money in software fees. 2. Talking about z /OS pages <ul><li>Page is a set of contiguous 4K virtual addresses…
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  • 1. DB2 V8 Bufferpool Pagefixing For saving money in software fees.
  • 2. Talking about z /OS pages <ul><li>Page is a set of contiguous 4K virtual addresses aligned at 4K boundary. Do you know that now we have 1M pages?Pages are virtually located in address spaces. </li></ul><ul><li>A page is created through the Virtual Storage Management functions: G ETMAIN and IEARV64. </li></ul><ul><li>Parameters define the AS locality of the new born page: </li></ul><ul><li>AS private area below the line </li></ul><ul><li>AS private area above the line </li></ul><ul><li>AS private area above the bar </li></ul><ul><li>A page also can be located in Dataspace s and Hiperspace s </li></ul>
  • 4. GETMAIN Macro GETMAIN LC,LA=length addr,A=addr LU,LA=length addr,A=addr VC,LA=length addr,A=addr VU,LA=length addr,A=addr EC,LV=length value,A=addr EU,LV=length value,A=addr VRU,LV=(maximum length value, minimum length value) SP=subpool nmbr
  • 6. What is Pagefixing <ul><li>Physically the contents of a page may reside in a central storage 4KB frame or in 4KB slot in a page data set (see STOR and STORF MN III RMF reports). </li></ul><ul><li>Fixing a page means that this page is not available to be stolen from a frame to a slot. There is a noticeable CPU cycles for fixing the page. </li></ul><ul><li>Why do we need to page fixing? </li></ul><ul><li>Integrity in general , an example could be I/O b uffer fixing </li></ul>
  • 7. DB2 Bufferpools DB2 Bufferpool is a set of same size I/O buffers in virtual storage. Each buffer contains a DB2 page. The full Bufferpool is contained in z/OS pages (confuse?). DB2 Bufferpools are used to avoid I/O operations in random accesses and to make them more efficient for sequential access. DB2 Bufferpool can be located in the three private areas in an AS or Dataspaces or Hiperspaces (not recommended). Buffers from the Bufferpool must be fixed before any I/O operation and free after the I/O operation end. Those functions consumes lots of CPU cycles.
  • 10. Fixing DB2 V8 Bufferpools <ul><li>The idea here is to trade CPU cycles by central storage frames keeping DB2 buffers in some specific Bufferpools be permanently fixed. </li></ul><ul><li>We expected more than 20% DB2 CPU time savings impacting hardware saves and software saves (less MSUs/H). </li></ul><ul><li>It is strongly recommended after taking this option to track central storage performance indicators as: Highest UIC, Page Fault Rate, Available Queue size. Also it is recommended to increase the number of available slots. </li></ul>
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