Expert Oracle Exadata - Parent Directory

CHAPTER 3 HYBRID COLUMNAR COMPRESSIONSUM(PK_COL)-----------6.1800E+151 row selected.Elapsed: 00:00:04.78Table 3-4 shows the timings for the unqualified query in a tabular format.Table 3-4. Unqualified Query Timing on SKEW3Table Name Compress For Compression Ratio Run Time Run Time RatioSKEW3 6.21SKEW3_OLTP OLTP 1.4 5.79 0.93SKEW3_BASIC BASIC 1.6 5.26 0.85SKEW3_HCC1 QUERY LOW 4.0 3.56 0.57SKEW3_HCC2 QUERY HIGH 45.6 3.39 0.55SKEW3_HCC3 ARCHIVE LOW 45.6 3.36 0.54SKEW3_HCC4 ARCHIVE HIGH 55.9 4.78 0.77The query does not require a lot of CPU resources on the DB server. As a result, the savings in I/Otime more than offset the increased CPU. Note that the rather significant CPU requirements of theARCHIVE HIGH decompression caused the elapsed time to increase for this test over the less CPUintensivealgorithms. Nevertheless, it was still faster than the uncompressed run. Here’s a snapshot oftop output while one of these queries was running.top - 15:37:13 up 4 days, 7:14, 9 users, load average: 5.00, 2.01, 2.50Tasks: 867 total, 7 running, 860 sleeping, 0 stopped, 0 zombieCpu(s): 25.2%us, 0.9%sy, 0.0%ni, 73.4%id, 0.5%wa, 0.0%hi, 0.1%si, 0.0%stMem: 74027752k total, 35193896k used, 38833856k free, 346568k buffersSwap: 16771852k total, 568488k used, 16203364k free, 29976856k cachedPID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND25414 oracle 16 0 10.0g 40m 31m S 33.0 0.1 0:13.75 ora_p001_SANDBOX125474 oracle 15 0 10.0g 39m 30m S 32.4 0.1 0:13.54 ora_p012_SANDBOX125472 oracle 15 0 10.0g 37m 29m S 28.8 0.1 0:13.45 ora_p011_SANDBOX125420 oracle 16 0 10.0g 35m 28m R 27.8 0.0 0:13.71 ora_p004_SANDBOX125418 oracle 15 0 10.0g 39m 31m R 27.4 0.1 0:13.78 ora_p003_SANDBOX125435 oracle 15 0 10.0g 38m 30m S 27.4 0.1 0:13.46 ora_p008_SANDBOX125478 oracle 15 0 10.0g 38m 30m S 27.1 0.1 0:13.75 ora_p014_SANDBOX125428 oracle 15 0 10.0g 38m 31m S 24.8 0.1 0:13.81 ora_p005_SANDBOX182