In oracle db, the calculation formula of a data dictionary pct miss is oraclepct.

In oracle db, the calculation formula of a data dictionary pct miss is oraclepct.

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Http://blog.csdn.net/msdnchina/article/details/38766801

 

The data dictionary mentioned in this article uses dc_histogram_defs as an example to describe the calculation formula of dc_histogram_defs.

Dc_histogram_defs is the definitions of the histogram.

The db used in is oracle 10.2.0.4

 

In the oracle production database, the data in one of my tables has 1 billion rows of records. How can we quickly calculate the number of rows? Don't tell me the answer using count (*).

Oracle has a data dictionary table that records the number of rows after analysis. It looks like all_tables.

Differences between control files and data dictionaries in oracle

Control File: as the name suggests, it is mainly used to control oracle. There are various parameters in it. It is recommended that you do not modify them.
Data Dictionary: as its name implies, it mainly stores information about various oracle Systems. It serves as a dictionary. DBAs must be able to use the data dictionary to understand the situation of oracle and identify problems.

Do you understand?