MIS 561 Week 4 Midterm Collection

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MIS 561 Week 4 Midterm Collection

(TCO 1) We know that a DBA (Database Administrator) should have knowledge of database structures, such as tables and SQL. List and describe at least four other categories of tasks expected from a DBA.

A DBA must ensure that:

databases are useful, usable, available, and correct.there is database performance, monitoring, and tuning.there is access authorization and security.there is database backup and recovery.there are interfaces with databases.(TCO 2) Before a newly installed DBMS can be used effectively, standards and procedures must be developed for database usage. Name some of these standards that, if practiced, could help in reducing cost of supporting end users.

Your Answer:

Standards are common practices that ensure the consistency and effectiveness of the database environment, such as database naming conventions. Procedures are defined, step-by-step instructions that direct the processes required for handling specific events, such as a disaster recovery plan. Failure to implement database standards and procedures will result in a database environment that is confusing and difficult to manage.

The DBA should develop database standards and procedures as a component of corporate-wide IT standards and procedures. They should be stored together in a central location as a printed document, in an online format, or as both. Several vendors offer canned standards and procedures that can be purchased for specific DBMS products.

(TCO 3) Designing and implementing a physical database from a logical data model is not just a simple matter of mapping entities to tables, attributes to columns, and relationships to referential constraints.Quite a few other database design issues must be addressed. Effective storage planning is part of the physical process design. As a DBA, how do you calculate the amount of storage space usage required to store a table?

Your Answer:

To calculate the amount of storage required to store a table, the DBA must first establish the row size. This is accomplished by adding up the maximum size of all of the columns, based on their assigned data type and length. An average size can be substituted for variable-length columns.An estimate for the number of bytes required can be calculated by multiplying the row size by the number of rows planned to be stored in the table. Of course, the DBA must also factor in any storage overhead required by the DBMS for things like row and page headers, pointers, and the like. Because each DBMS uses different techniques, each DBMS will have different overhead requirements.

TCO 4) When implementing a physical database from a logical data model, you must consider database performance by allowing data in the database to be accessed more rapidly. One way to improve performance is to reduce the number of input/output when requesting data from a database. Which method do you recommend for possible reduced I/O when querying chunks of data? How does it improve

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the amount of input/output and what are the disadvantages of the method?

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Your Answer:

An access request using an index can perform better than a table scan because the requested data can be accessed directly using the pointers from the leaf node of the index. This reduces I/O and enhances performance for most data access requests. If you need to retrieve ranges of data, hashing is not optimal because the data will be spread out instead of clustered, and therefore, I/O costs will be substantial. Additionally, hashing requires a unique key to minimize collisions. So, hashing should be considered only when an overwhelming majority of the queries against the table are based on lookups using the key and will return small result sets.

(TCO 5) What is a lock in a database and what does it accomplish?

Your Answer:

The DBMS uses a locking mechanism to enable multiple, concurrent users to access and modify data in the database. By using locks, the DBMS automatically guarantees the integrity of data.The DBMS locking strategies permit multiple users from multiple environments to access and modify data in the database at the same time. Locks are used to ensure the integrity of data.When a database resource is locked by one process, another process is not permitted to change the locked data. Locking is necessary to enable the DBMS to facilitate the ACID properties of transaction processing.

As a DBA, you are asked to add a column in the middle of an existing table that is already populated with data. What steps do you take in accomplishing this task? With what factors are you concerned?

Your Answer:

To accomplish such a task, the DBA must drop the table and recreate it with the new column in the middle. But what about the data? When the table is dropped, the data are deleted unless the DBA was wise enough to first unload the data. But what about the indexes on the table? Well, they too are dropped when the table is dropped, so unless the DBA knows this and recreates the indexes too, performance will suffer. The same is true for database security: When the table is dropped, all security for the table is also dropped. And this is but one example of a simple change that becomes difficult to implement and manage. Adding to this dilemma is the fact that most organizations have at least two, and sometime more, copies of each database. At the very least, a test and production version will exist.

(TCO 7) Downtime is not tolerated by some businesses. The cost of downtime varies from business to business. Which factors do you consider when estimating the cost of downtime?

When estimating the cost of downtime, remember to factor in all of the costs, including lost business during the outage.cost of catching up after systems are once again available.legal costs of any lawsuits.impact of reduced stock value (especially for dotcoms that rely on computerized systems for all of their business).

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Additionally, downtime can negatively impact a company’s image. In this day and age, an outage of any length that impacts business, particularly e-business, will be reported by the press—and if the story is big enough, not just the computer press, but the business press as well. Let’s face it, bad news travels fast. Recovering from negative publicity can be a difficult, if not impossible, task.(TCO 2) Each of the major DBMS products changes quite rapidly, and keeping DBMS software up-to-date can be a difficult task. As a DBA, what are the issues to consider when upgrading to a new DBMS version to have little or no disruption?

Your Answer:

A DBMS version upgrade can be thought of as a special case of a new installation. All of the procedures required of a new installation apply to an upgrade: you must plan for appropriate resources, reconsider all system parameters, and ensure that all supporting software is appropriately connected. However, another serious issue must be planned for: existing users and applications. An upgrade needs to be planned to cause as little disruption to the existing users as possible. Furthermore, any additional software that works with the DBMS (such as purchased applications, DBA tools, utilities, and so on) must be verified to be compatible with the new DBMS version.

(TCO 5) What is a COMMIT in a database and what does it accomplish?

Your Answer:

The results of running a transaction will record the effects of a business process—a complete business process. The data in the database must be correct and proper after the transaction executes.When all of the steps that make up a specific transaction have been accomplished, a COMMIT is issued. The COMMIT signals that all work since the last COMMIT is correct and should be externalized to the database. At any point within the transaction, the decision can be made to stop and roll back the effects of all changes since the last COMMIT.

(TCO 1) What are the duties of a system administrator (SA) in regards to a database, and how are a DBA’s (Database Administrator) responsibilities different from an SA when supporting a database?

Your Answer:

A system administrator role is IT infrastructure and has typically no responsibility for the database design and support. The SA is responsible for networking protocols, operating systems parameters, message queuing software and ensuring that IT infrastructure is operational for database development. Setting up the DBMS and applying the vendor maintenance and migration to new DBMS releases and versions are tasks of SA. The DBA is responsible for the database, and the SA is responsible for DBMS installation, modification, and support.

(TCO 2) Suppose that as a DBA, you are tasked with installing a new database management system in your organization. Would you choose the default system parameters when installing the system software?Explain and support your answer with reasoning.

Your Answer: