Expert Oracle Exadata - Parent Directory

CHAPTER 3 HYBRID COLUMNAR COMPRESSIONBLOCKS : 15225910EMPTY_BLOCKS : 0AVG_SPACE : 0AVG_ROW_LEN : 917MONITORING: YESSAMPLE_SIZE : 114736686TOTALSIZE_MEGS : 120019=====================================================================================So the number of rows is not that great, only about 115 million, but the table is wide. It has 161columns and the average row length is 917 bytes. It is a bit of a mixed bag with regards to compressibilitythough. Many of the columns contain a high percentage of nulls. On the other hand, many of thecolumns have a very low number of distinct values. This table may be a candidate for reordering the dataon disk as a strategy to improve the compression ratio. At any rate, here are the compression ratesachieved on this table at the various HCC levels.SYS@POC1> @comp_ratioEnter value for original_size: 120019Enter value for owner: KSOEnter value for table_name: REV_ACCRUAL_HCC%Enter value for type:OWNER SEGMENT_NAME TYPE TOTALSIZE_MEGS COMPRESSION_RATIO---------- -------------------- ------------------ -------------- -----------------KSO REV_ACCRUAL_HCC1 TABLE 31,972.6 3.8KSO REV_ACCRUAL_HCC2 TABLE 17,082.9 7.0KSO REV_ACCRUAL_HCC3 TABLE 14,304.3 8.4KSO REV_ACCRUAL_HCC4 TABLE 12,541.6 9.6--------------sum 75,901.4Retail Sales DataThe final table is made up of sales figures from a retailer. The table contains about 6 billion records andoccupies well over half a Terabyte. There are very few columns, and the data is highly repetitive. In fact,there are no unique fields in this table. This is a very good candidate for compression. Here are the basictable statistics:==========================================================================================Table Statistics==========================================================================================TABLE_NAME: SALESLAST_ANALYZED : 23-DEC-2010 03:13:44DEGREE : 1PARTITIONED: NONUM_ROWS : 5853784365CHAIN_CNT : 0BLOCKS : 79183862EMPTY_BLOCKS : 0AVG_SPACE : 0AVG_ROW_LEN : 93MONITORING: YES98