SPATIAL DATABASES

There are important differences in terms of resource needs between DBMS, SDBM and programming applications:

	CPU Cost	I/O Cost
DBMS	low	high
C Program	high	low
SDBMS	high	high

Components involved in the management of data in the secondary memory are:

• Buffer Manager: It is a software module within the DBMS in charge of management the transfer of data between main and secondary memory. It must ensure that a transaction is not suspended because the data is not in main memory. To do so, it defines replacement policies such a LRU (least recently used) and query locality set model (QLSM).

 

• Field, Record and Files:

• File Structure. It refers to the organization of records in the file. In an unordered file, a search by a key requires to scan all records. In the worst case, it checks all records (pages) in the file. More sophisticated file organizations include hashed file and ordered files. In the spatial domain, clustering is a kind of ordering or grouping of data with goal of reducing the seek and latency time. Another strategy for file organization is to handle an indexing structure (different from the file itself) that guides the search process.In such case, the records in the file are also ordered and linked to access entries in the indexing structures.

   

 

 

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