4.1 Data Dependency Terminologies
Because our overall goal is to discover data dependencies that are related to sequence of operations performed by transactions, we first define sequence in our context.
Definition 1: A sequence is an ordered list of read and/or writes operations. We denote a sequence s by , where oi ∈ {r, w} and dk is a data item, 1 ≤ k ≤ n. D(s) represents the set of data items contained in the sequence, i.e., D(s) = {d1, d2, …, dn}. The support for a sequence is defined as the fraction of total transactions that contains this sequence.
Read sequence and write sequence are employed to define read and write dependencies respectively.
Definition 2: The Read Sequence of data item x is the sequence with the format which represents that the transaction may need to read all data items d1, d2, …, dn in this order before the transaction updates data item x. It must be noted that each data item may have several read sequences each having different length. All these sequences together are called Read Sequence Set of this data item.
The notation rs(x) is used to denote the read sequence set of data item x. For example, consider the following update statement in a transaction.
Update Table1 set x = a + b + c where d = 90;
In this statement, before updating x, values of a, b, c and d must be read and then the new value of x is calculated. So rs(x).
It must be noted that the database log only contains before and after images of x instead of the mathematical operation used for calculating x, i.e., x = a + b + c. The above example is only for illustrating the concept of read sequence. The database log containing the above transaction ma...
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...A pre-set threshold is used to identify whether a dependency is weak or strong.
For example, suppose the predefined threshold for weight of data dependency is 40%. For the sequence , if the probability of reading {a, b, c, d} before x is updated is 75%, then r weight(x , {a, b, c, d}) is equal to 75%. Since this is larger than the threshold, we say, the dependency between x and {a, b, c, d} is strong.
Figure 1 illustrates an example data dependency. Data item x has read dependency relationships with {a, b, c, d}, {c, d}, and {x, e, f}. Besides, it has write dependency relationships with {y, z} and {u, v}. Suppose the predefined threshold for weight of data dependency is 40%. Then for the read dependency only {a, b, c, d} has strong data dependency with x. Similarly for the write dependency only {u, v} has strong data dependency with x.
https://datatracker.ietf.org/doc/rfc2710/?include_text=1
2) Analyze the graph that compares the Segment Sequence numbers of the three scenarios. Why does the Drop_NoFast scenario have the slowest growth in sequence numbers?
The Data XML contains the data that needs to be added/updated to/deleted from the Database.
Starvation can occur in systems where the selection of victims is based primarily on cost factors, that is, there is a high possibility that the same transaction is always picked as a victim. The downside to this is that this transaction may never get to complete its designated task, leading to the issue of starvation. Therefore, mechanisms must be put in place to ensure that transaction can be picked as a victim only a (small) finite number of times. Including the number of rollbacks in the cost factor is a common strategy used to deal with the issue.
Also, the value of the variable may differ depending on the assignment statement. For example, if we have the assignment statement as,
In order to prevent both intentional and unintentional alteration, and destruction of information, any software application needs controls to ensure the reliability of data. Here are two specific controls per each one of the three data control categories, and how each control contributes to ensuring the data reliability in the format requested.
Completeness: All documents are identified with a unique number and have a numerical sequence checked.
Oracle ThinkQuest. Oracle Education Foundation, 04 Jun 2010. Web.
Chaffey et al., (2003) identifies the following components of the transaction processing system. The first one is the data entry. Usually it is implemented with the help of bar-code techniques and magnetic charts. In the database of dentist clinic, the information is entered using a computer keyboard and mouse. The second one is the storage and search for information in the database management system (DBMS). Microsoft Access allows saving data after input, change them as needed and find any available information. The third component is the admittance to data throw the reporting online and offline, where the last one saves records in another system for deep analyzing. In the database of dentist clinic, Microsoft Access is able to create the reports based on the queries, moderate them in a proper way and provide to managers for subsequent monitoring.
The dependent variables rely on the independent variables:
In case of detecting some errors, correcting entries are made to correct them or invert their effect before proceeding to the next step.
"Although fully searchable text could, in theory, be retrieved without much metadata in the future, it is hard to imagine how a complex or multimedia digital object that goes into storage of any kind could ever survive, let alone be discovered and used, if it were not accompanied by good metadata" (Abby Smith). Discuss Smith's assertion in the context of the contemporary information environment
[1]- Ralph Stair, George Reynolds and Thomas Chesney. 2012. Fundamentals of Business information systems. 2nd edition: Cengage Learning EMEA.
Section 3) to extract meaning or context from the data in order to perform tasks in the