1. A method for accessing a set of data tables in a source database, comprising: providing, by a processor of a computing system, a set of table categories for tables in the source database; providing, by the processor, a set of metrics, each metric comprising a respective characteristic metric for each table category, wherein the providing of the set of metrics includes: generating, by the processor, from the set of data tables, multiple probe tables having each of the table categories, identifying, by the processor, characteristics for every table category after analyzing the multiple probe tables, and determining, by the processor, metrics associated with threshold values for each table category based on the identified characteristics of the multiple probe tables; for each table of the set of the data tables: evaluating, by the processor, the set of metrics, analyzing, by the processor, the evaluated set of metrics, and categorizing, by the processor, each table into one of the set of table categories using a result of the analysis; outputting, by the processor, information indicative of each table category of each table of the set of data tables; in response to the outputting of the information indicative of each table category of each table of the set of data tables, receiving, by the processor, a request to select data tables of the set of data tables according to a part of the set of table categories for extraction, transformation, and loading (ETL) processing; selecting, by the processor, a subset of data tables of the set of data tables using the set of table categories for performing the ETL processing on the subset of data tables; and performing, by the processor, the ETL processing on the source database using the selected subset of the data tables in the source database as input; wherein evaluating the set of metrics includes evaluating the set of metrics using a predetermined first set of statistics, the predetermined first set of statistics comprising a first part and a second part, wherein determining the predetermined first set of statistics comprises: calculating the first part of the predetermined first set of statistics using the set of tables; requesting monitoring data of the source database; receiving the monitoring data; and generating the second part of the predetermined first set of statistics using the monitoring data.