PLSQL Architecture

Therefore, PL/SQL can reside in two environments, which are-

• Oracle Server
• Oracle tools

These two environments are independent of each other. PL/SQL engine accepts any valid PL/SQL block as an input.



Application Server development tools, which lacks a local PL/SQL engine must rely on Oracle to process PL/SQL blocks and subprograms.

 

The Server passes the blocks and subprograms to its local PL/SQL engine.

 

PL/SQL programs are written as the lines of text, using a specific set of the characters. PL/SQL character set includes-

• The upper and lower case letter A..Z, a..z
• The number 0…9
• Tabs, spaces and carriage returns.
• The symbols () + - * / ! ; : ‘ # ^ & {} [] ?

PL/SQL is not case-sensitive, so lower case letter is equivalent to corresponding upper-case letter.

Reserved words have special syntactic meaning to PL/SQL, so it cannot be redefined.

Lexical units may be separated by one or more spaces or other delimiters, which would not be confused as part of the lexical unit.

A delimiter is a simple or compound symbol, which has a special meaning to PL/SQL. Delimiters can be used to represent an arithmetic operation such as addition and subtraction.

Identifiers can be used to name PL/SQL program objects and the units, which includes constants, variables, exceptions, cursors, subprograms and packages. Identifiers must start alphabetically and may contain up to 30 characters.

Character and date literals must be enclosed in single quotes. Numeric literals are of two kinds integer and real’s.

An integers literals is an optionally signed whole number without a decimal point. E.g. 987, -675.

A real literal is an optionally signed whole or fractional number with a decimal point. E.g. 8.76, -4.67.

Thus, we learnt, PL/SQL runtime system is a technology and an independent product. This technology is actually like an engine, which executes PL/SQL blocks and subprograms.