Oracle Alert is your complete exception control solution. Alerts signal important or unexpected activity in your database. They ensure that you are regularly and quickly informed about critical database events instead of sorting through length reports.
The basic function of alerts includes but not limited to

  1. Keep you informed of critical activity in your database
  2. Deliver key information from your applications, in the format you choose
  3. Provide you with regular reports on your database information
  4. Automate system maintenance, and routine online tasks

Alerts keep a constant check on your database information and prompt you when the specified criteria are met. You can use either an Oracle application or a custom oracle application to define alerts. However, few applications such as purchasing, allow you to simply activate and use alerts supply by default.
You can define one of two types of alerts: an event alert or a periodic alert.
An event alert immediately notifies you of activity in your database as it occurs. When you create an event alert, you specify the following:

  • A database event that you want to monitor, that is, an insert or an update to a specific database table.
  • A SQL Select statement that retrieves specific database information as a result of the database event.
  • Actions that you want Oracle Alert to perform as a result of the database event. An action can entail sending someone an electronic mail message, running a concurrent program, running an operating script, or running a SQL statement script. You include all the actions you want Oracle Alert to perform, in an action set.

A periodic alert, on the other hand, checks the database for information according to a schedule you define. When you create a periodic alert, you specify the following:

  • A SQL Select statement that retrieves specific database information.
  • The frequency that you want the periodic alert to run the SQL statement.
  • Actions that you want Oracle Alert to perform once it runs the SQL statement. An action can entail sending the retrieved information to someone in an electronic mail message, running a concurrent program, running an operating script, or running a SQL statement script. You include all the actions you want Oracle Alert to perform, in an action set

By creating event alerts, you can have an immediate view of the activity in your database, so you keep on top of important or unusual events as they happen. By creating periodic alerts, you can have current measurements of staff and organization performance, so you can zero in on potential trouble spots. You can automate routine transactions, preserving your valuable time for more important issues. Oracle Alert gives you the information you need online, so you do not have to contend with a pile of paperwork.
Workflow vs Alerts
Unlike alerts, workflow is defined in a system to detect a condition and requires user intervention. Every time a response is not recorded during a designated time period, workflow may send a notification to the user’s manager depending upon the workflow definition. It is difficult to accomplish such notification using alerts.

PL/SQL stands for Procedural Language extension of SQL.
PL/SQL is a combination of SQL along with the procedural features of programming languages. It was developed by Oracle Corporation in the early 90’s to enhance the capabilities of SQL.
PL/SQL Environment
PL/SQL is not an Oracle product in its own right; it is a technology used by the Oracle server and by certain Oracle tools. Blocks of PL/SQL are passed to and processed by a PL/SQL engine, which may reside within the tool or within the Oracle server. The engine that is used depends on where the PL/SQL block is being invoked from. When you submit PL/SQL blocks from a Oracle precompiler such as Pro*C or Pro*Cobol program, userexit, iSQL*Plus, or Server Manager, the PL/SQL engine in the Oracle Server processes them. It separates the SQL statements and sends them individually to the SQL statements executor.

A single transfer is required to send the block from the application to the Oracle Server, thus improving performance, especially in a client-server network. PL/SQL code can also be stored in the Oracle Server as subprograms that can be referenced by any number of applications connected to the database.
Many Oracle tools, including Oracle Developer, have their own PL/SQL engine, which is independent of the engine present in the Oracle Server. The engine filters out SQL statements and sends them individually to the SQL statement executor in the Oracle server. It processes the remaining procedural statements in the procedural statement executor, which is in the PL/SQL engine. The procedural statement executor processes data that is local to the application (that is, data already
inside the client environment, rather than in the database). This reduces the work that is sent to the Oracle server and the number of memory cursors that are required.
Advantages of PL/SQL
These are the advantages of PL/SQL.
Block Structures: PL SQL consists of blocks of code, which can be nested within each other. Each block forms a unit of a task or a logical module. PL/SQL Blocks can be stored in the database and reused.
Procedural Language Capability: PL SQL consists of procedural language constructs such as conditional statements (if else statements) and loops like (FOR loops).
Better Performance: PL SQL engine processes multiple SQL statements simultaneously as a single block, thereby reducing network traffic.
Error Handling: PL/SQL handles errors or exceptions effectively during the execution of a PL/SQL program. Once an exception is caught, specific actions can be taken depending upon the type of the exception or it can be displayed to the user with a message.
The PL/SQL language is a robust tool with many options. PL/SQL lets you write code once and deploy it in the database nearest the data. PL/SQL can simplify application development, optimize execution, and improve resource utilization in the database.
The language is a case-insensitive programming language, like SQL. This has led to numerous formatting best practice directions. Rather than repeat those arguments for one style or another, it seems best to recommend you find a style consistent with your organization’s standards and consistently apply it. The PL/SQL code in this book uses uppercase for command words and lowercase for variables, column names, and stored program calls
PL/SQL also supports building SQL statements at run time. Run-time SQL statements are dynamic SQL. You can use two approaches for dynamic SQL: one is Native Dynamic SQL (NDS) and the other is the DBMS_SQL package. The Oracle 11g Database delivers new NDS features and improves execution speed. With this release, you only need to use the DBMS_SQL package when you don’t know the number of columns that your dynamic SQL call requires. Chapter 11 demonstrates dynamic SQL and covers both NDS and the DBMS_SQL package.

PL/SQL is a procedural language that Oracle developed as an extension to standard SQL to provide a way to execute procedural logic on the database.

SQL, SQL*Plus, PL/SQL: What’s the Difference?
This question has bedeviled many people new to Oracle. There are several products with the letters “SQL” in the title, and these three, SQL*Plus, SQL, and PL/SQL, are often used together. Because of this, it’s easy to become confused as to which product is doing the work and where the work is being done. This section briefly describes each of these three products.

SQL stands for Structured Query Language. This has become the lingua franca of database access languages. It has been adopted by the International Standards Organization (ISO) and has also been adopted by the American National Standards Institute (ANSI). When you code statements such as SELECT, INSERT, UPDATE, and DELETE, SQL is the language you are using. It is a declarative language and is always executed on the database server. Often you will find yourself coding SQL statements in a development tool, such as PowerBuilder or Visual Basic, but at runtime those statements are sent to the server for execution.


PL/SQL is Oracle’s Procedural Language extension to SQL. It, too, usually runs on the database server, but some Oracle products such as Developer/2000 also contain a PL/SQL engine that resides on the client. Thus, you can run your PL/SQL code on either the client or the server depending on which is more appropriate for the task at hand. Unlike SQL, PL/SQL is procedural, not declarative. This means that your code specifies exactly how things get done. As in SQL, however, you need some way to send your PL/SQL code up to the server for execution. PL/SQL also enables you to embed SQL statements within its procedural code. This tight-knit relationship between PL/SQL, SQL, and SQL*Plus is the cause for some of the confusion between the products.

SQL*Plus is an interactive program that allows you to type in and execute SQL statements. It also enables you to type in PL/SQL code and send it to the server to be executed. SQL*Plus is one of the most common front ends used to develop and create stored PL/SQL procedures and functions.

What happens when you run SQL*Plus and type in a SQL statement? Where does the processing take place? What exactly does SQL*Plus do, and what does the database do? If you are in a Windows environment and you have a database server somewhere on the network, the following things happen:
   1. SQL*Plus transmits your SQL query over the network to the database server.
   2. SQL*Plus waits for a reply from the database server.
   3. The database server executes the query and transmits the results back to SQL*Plus.
   4. SQL*Plus displays the query results on your computer screen.

Even if you’re not running in a networked Windows environment, the same things happen. The only difference might be that the database server and SQL*Plus are running on the same physical machine. This would be true, for example, if you were running Personal Oracle on a single PC.

PL/SQL is executed in much the same manner. Type a PL/SQL block into SQL*Plus, and it is transmitted to the database server for execution. If there are any SQL statements in the PL/SQL code, they are sent to the server’s SQL engine for execution, and the results are returned back to the PL/SQL program.