Libraries 
As a transfer structure to Report Painter (BC-SRV-REP) or Report Writer (BC-SRV-REP) you use a reporting table, which is defaulted by SAP and cannot be maintained. The reporting table is a logical view of different database tables and includes all characteristics, basic key figures, and (predefined) key figures (= these were predefined columns).
Example
In Cost Center Accounting, reporting table CCSS is used as the transfer structure.
Reporting table RWCOOM is also available for special totals record reports in overhead controlling (see also: Defining Reports For Overhead Cost Controlling).
Features
In a library, you collect the characteristics, basic key figures, and predefined columns from the report table, which you need for your Report Painter or Report Writer reports. The table name is stored in the header of each library.
Characteristics are non-numerical fields. They represent criteria with which you can select data records. Examples of characteristics are the controlling area and fiscal year.
Basic key figures are numeric fields, which can be evaluated in a report. Examples include overall costs and activity quantities.
Key figures consist of a basic key figure and one or more characteristics. They are used for the fast definition of frequently-used columns. Examples include total actual costs for the current fiscal year or plan fixed costs for the previous fiscal year.
Note
A report can only be generated using characteristics, basic key figures, and key figures from the library assigned to the report.
The following graphic illustrates how libraries work in the SAP System.
In library maintenance, you can assign a newly defined library to a table. You also define the allowed characteristics, basic key figures and key figures. The SAP system provides an overview of each of the three categories in which you can select the objects allowed for a given library.
By entering the item in the Item column, you can determine:
Which order characteristics, basic key figures and key figures are displayed in the selection lists of the report painter
This allows you to place any entries commonly used in reports at the beginning of the selection list.
In which order report parameters (Values selection) and the report objects (Sets selection) (for example, cost centers, cost elements) are displayed on the selection screen in report painter reports
NoteIf you select objects without positioning or with position “0”, the system does not offer the objects with the report definition using Report Painter. However, you can use these characteristics in Report Writer reports.
End of the note. ExampleThe standard reports delivered with Cost Center Accounting are summarized in the following libraries.
All reports for cost accounting methods based exclusively on the full costs method are located in the 1VK library.
For methods that also take marginal costs (CO) into account, there are special reports located in the 1GK library in addition to the reports found in the 1VK library.
For variance (CO) analyses, use the 1AB library.
For summarization (CO-PC) reports, use the 1RU library.
End of the example. NoteStandard libraries 1C1 and 101 have not been supported since Release 2.1. The standard reports for these libraries have been deleted. The system still includes libraries 1C1 and 1O1 so that user-defined reports based on these libraries can continue to be used.
End of the note.
Activities
To create, display or maintain a library, call up the relevant Controlling (CO) component and choose 
Information System 
Tools Report Painter Report Writer Library Display/Create/Change/Delete 
.
Choose
Utilities Catalog to display an overview of all libraries for a table.Choose
Extras Use to generate a list of the reports assigned to the selected library.Choose Goto Header, Characteristics, Basic key figures or Key figures to edit these library functions.
In maintenance or in the display of basic key figures or characteristics, choose Documentation to call up description of previously selected basic key figures and characteristics.
For more information, see the SAP Library for SAP ERP Central Component on the SAP Help Portal at http://help.sap.com Accounting Financial Accounting (FI) Special Purpose Ledger Information System Report Painter / Report Writer Libraries .