a0006 03 essential unix and linux for the oracle db morebook vn 1702
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Revision no.: PPT/2K403/02
Essential Unix (and Linux) for the Oracle
DBA
Revision no.: PPT/2K403/02
Architecture of UNIX Systems
2
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Revision no.: PPT/2K403/02
UNIX System Structure
3
•
Operating system interacts directly with Hardware
•
Provides common services to programs
•
Insulating from Hardware
•
Kernel is treated as an operating system
•
Programs are independent of the Hardware
•
Easy to move on different processing environment
ã
Programs should be independent of Hardware
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Revision no.: PPT/2K403/02
UNIX System Structure
(contd.)
4
•
Programs in the upper layer communicate with Kernel using
defined set of system calls
•
System calls instruct the Kernel to do various operations
•
System calls also exchange the data between Kernel and
program
•
Some Standard programs also fall in this layer i.e. executable
files by C compiler
•
Top most layer is used for other application programs eg. C
compiler (CC)
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Revision no.: PPT/2K403/02
SHELL
5
•
It is a program that interprets the commands.
•
If the command is valid then the shell directs the kernel to
carry out the request
•
If invalid then an error message is displayed.
•
Shell starts when an user logs in, and terminates when the
user logs out.
•
Presence of shell is indicated by a special symbol known as
the shell prompt ( $ or # ).
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Revision no.: PPT/2K403/02
The Crontab and Automation of Scripts
47
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Revision no.: PPT/2K403/02
48
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