Expert Oracle Exadata - Parent Directory

CHAPTER 11 UNDERSTANDING EXADATA PERFORMANCE METRICSNAMECLASS_NAME---------------------------------------------------------------- ----------EHCC Analyze CUs DecompressedDEBUGEHCC Analyzer CallsDEBUGEHCC Archive CUs CompressedDEBUGEHCC Archive CUs DecompressedDEBUGEHCC CU Row Pieces CompressedDEBUGEHCC CUs CompressedDEBUGEHCC CUs DecompressedDEBUGEHCC Check CUs DecompressedDEBUGEHCC Columns DecompressedDEBUGEHCC Compressed Length CompressedDEBUGEHCC Compressed Length DecompressedDEBUGEHCC DML CUs DecompressedDEBUGEHCC Decompressed Length CompressedDEBUGEHCC Decompressed Length DecompressedDEBUGEHCC Dump CUs DecompressedDEBUGEHCC Normal Scan CUs DecompressedDEBUGEHCC Pieces Buffered for DecompressionDEBUGEHCC Query High CUs CompressedDEBUGEHCC Query High CUs DecompressedDEBUGEHCC Query Low CUs CompressedDEBUGEHCC Query Low CUs DecompressedDEBUGEHCC Rowid CUs DecompressedDEBUGEHCC Rows CompressedDEBUGEHCC Rows Not CompressedDEBUGEHCC Total Columns for DecompressionDEBUGEHCC Total Pieces for DecompressionDEBUGEHCC Total Rows for DecompressionDEBUGEHCC Turbo Scan CUs DecompressedDEBUGAll the statistics starting from cell are, as the name says, related to storage cells. These stats are measuredand maintained by cells themselves and then sent back to the database sessions during any interactionover IDB protocol. Every database session receives the cell statistics along with the replies from theircorresponding cell sessions and then updates the relevant database V$ views with it. This is how theOracle database layer has insight into what’s going on in the “black box” of a cell, like the real number ofI/O operations done, the number of cell flash cache hits, and so on. Note that there are a few chainedrows […] cell statistics, which apparently use a different naming convention, having the “cell” in the endof the statistic name.Exadata Performance Counter ReferenceThis section explains some of the more important and interesting statistics in this chapter, although ifyou are lucky, you won’t have to dig down this deep in your troubleshooting; wait events and the SQLmonitoring feature are good enough for most basic troubleshooting and performance optimization.Nevertheless, understanding what’s behind these statistics and behavior will give you further insightinto Exadata internals and enable you to troubleshoot unusual performance problems more effectively.We’ll explain the stats in alphabetical order, to make it easier to use this section as a reference.356