Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
Saving Derived Attributes to Avoid Re-computation
As discussed, "redundancy means duplication of exact data". But, if multiple copies of same data are present in the system, then it can increase chance of availability of data, but the problem of computing overhead is also associated with it.
To overcome this difficulty we can "cache" or store the redundant data in its computed form and classes or objects might be defined to retain this information. The class which contains cached data must be updated if any of objects that it depends on are changed.
Figure shows use of derived object and derived attribute in OMTool. Each class box contains an ordered list of operations and attributes, each represented as text string (left of diagram). Given the location of the class box itself, the location of each attribute can be computed by adding up the size of all the elements in front of it. Since location of each element is required frequently, location of each attribute string is computed and then stored. The region containing entire attribute list is also computed and saved. In this way, you can avoid the testing of input points against the attribute text element. It is shown in the right side in Figures. If a new attribute string is added to list, then locations of the ones after it in list are simply offset by size of the new element.
Figure: Derived attribute to avoid re-computation
When is UPDATE_STATISTICS command used? - When processing of large data is done, this command is used. - Whenever large number of modification, deletions or copy takes place
Define According to the levels of abstraction, the schema at the intermediate level is called Ans: As per to the levels of abstraction, the schema at the intermediate level is
What is a data dictionary? Data Dictionary is a main source of data in a data management system. Its major function is to carry the creation and management of data definition
Conversion of entity sets: I) For every strong entity type E in the ER diagram, we make a relation R containing all the easy attributes of E. The relation R pri
Synonyms and Indexes Some of the essential properties of indexes are: An Index is a schema Object Indexes can be formed explicitly or automatically Indexes are m
limitations and benefits in database tecknowlagy
Define shadow paging. An alternative to log-based crash recovery method is shadow paging. This technique requires fewer disk accesses than do the log-based methods.
How external/conceptual mapping and conceptual /internal mapping is performed
Project Description: We have purchased facebook style chat software which we are using with our site. It is prepared in PHP but the rest of the site is developed asp.net. Iss
how to connect vb.net with access
Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd