You are here: Home / Systems / CERA / Data Model / CERA / Data_Access

Data_Access

Graph of CERA-2 Module DATA_ACCESS

Module_Access

MODULE_DATA_ACCESS-1.0.gif

click to enlarge

 

Download of CERA-2 Scheme graphs in different formats.

 

Overview

Information for automatted data access is provided by the module DATA_ACCESS. As the forms of storage can vary widely (e.g., data base, file system, tape library), DATA_ACCESS allows to define the structure of the locally used forms of storage in table Access_structure. Here the usage of the four variables storage_name in Storage is explained, where storage1_id to storage4_id point to.

For automatted data access it is often advisable to know, in what order the single data points are stored with respect to the five dimensions time, space, and topic (if more than one parameter is stored). To achieve this, in table Rec_structure dim1_type gives the type of the fastest varying variable, dim2_type of the second fastest and so on. The corresponding dim?_id points to the related record in one of the tables Scale, Time, Point_set or Para_order. Here Para_order is a locally defined table where the order of the topics can be stored, if necessary. If not all dimensions are used, their dim?_type and dim?_id values are set to 0 (zero).

The following examples are to clarify this.

 

Examples

PIK File System

Among others, a simple application of module DATA_ACCESS is run at PIK: only host name, directory, and file name are stored, using tables DATA_ACCESS, Access_structure, and Storage. This structure is described in table Access_structure, while the character strings are in Storage. DATA_ACCESS bundles both and keeps it, together with the date of their last modification.

DKRZ Blob Data

At DKRZ, binary large objects (blobs) are stored in a DBMS. The storage fields contain information on the data base and the name of a locally defined data base table, that gives more metadata on the specified blob.

Document Actions