Introduction To Sybase, Part 3
In our application, we use two databases. The first is the pubs2 example database. We use the titles table as the list of books. This table is read-only. We just view it; the application does not make changes to it. The second database is called book_d and it is created on two devices. The log segment is on device02 and has 10MB allocated to it. The data segment is on device01 and has 20MB allocated to it. There are five tables in this database.
inventory_t: this table is a one-to-one relationship to the titles table in the pubs2 database. There is one row in this table for each row in the titles table. This table contains the number of books in stock and the number on order.
orders_t: this table is a list of customer orders.
order_nbr_t: this table has one row in it. It is used to guarantee that the order number is always unique.
types_t: this table is a list of the types of books. It is used to populate the drop-down box on the search screen.
user_t: this table is a list of customers.
To provide access to the data, we use stored procedures in all cases except one. Stored procedures are SQL code stored in the database. This allows us to encapsulate procedures in the database so it doesn't have to be replicated in all your applications. It also provides a performance benefit. When the stored procedure is loaded, the SQL is precompiled. When the application runs, the server doesn't have to precompile the SQL, so the application should run faster. We used SQL in the search1 procedure, because it would change dramatically depending on the parameters given.
In the scripts, we have also created a user to access the database. Each time the CGI script runs, it logs in as this user. The end users of your application do not need to know this, and in fact, shouldn't know it. Even though this user has the minimum rights necessary to run the application, you should protect this user name and password.
This is a very small application. A few more things must be done if you put this application into production.
Make it look nicer. This application would have looked fine in the early 90's, but in today's world, it would need to look much better before people would use it.
Prepare and schedule automatic backups. Use cron to back up your data at regular intervals.
Prepare and schedule database consistency checks. These should be run regularly, again using cron to schedule these checks.
Create and tune table indexes. These tables have no defined indexes. An index is extra data about the table that will allow the database server to access the data faster.
Explaining how the database server uses indexes is beyond the scope of this article—I have a complete book on the subject. Before you put an application into production, you should load example data in all the tables and test queries to be run in your application. Based on the queries, you can make good guesses as to which indexes will be needed. There is a command in SQL that can help tune indexes. It is set showplan on. Entire book chapters are devoted to explaining this command and its output.
As you can see, using a Sybase database as the basis for your client-server applications is not a trivial task. The Sybase database server is an industrial-strength database, capable of handling hundreds of users and many gigabytes of data. Many databases are available for Linux. Of the free ones, I believe the Sybase database server is the most powerful. If you don't need a powerful database, there may be better choices. If, however, you need a high-power database to manage a large amount of data or many users, a Sybase database server would be a solid foundation.
Jay Sissom (email@example.com) is responsible for the web-based front end to the financial decision support data at Indiana University. He has installed and supported Sybase databases on many operating systems and has written database clients for the web. When not programming, he enjoys amateur radio and playing his bass guitar and keyboards.
Practical Task Scheduling Deployment
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
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|The Firebird Project's Firebird Relational Database||Jul 29, 2016|
|Stunnel Security for Oracle||Jul 28, 2016|
|SUSE LLC's SUSE Manager||Jul 21, 2016|
|My +1 Sword of Productivity||Jul 20, 2016|
|Non-Linux FOSS: Caffeine!||Jul 19, 2016|
|Murat Yener and Onur Dundar's Expert Android Studio (Wrox)||Jul 18, 2016|
- The Firebird Project's Firebird Relational Database
- Stunnel Security for Oracle
- My +1 Sword of Productivity
- Managing Linux Using Puppet
- Non-Linux FOSS: Caffeine!
- SUSE LLC's SUSE Manager
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- Parsing an RSS News Feed with a Bash Script
- Google's SwiftShader Released
- Doing for User Space What We Did for Kernel Space
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide