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LDS VSAM and DB2.
Posted: Fri Jan 17, 2014 4:59 pm
by Atif Alam
Hi,
DB2 is usually referred "as a good alternative to replace" VSAMs - but Db2 itslef uses LDS aas the underlying VSAM -- then why it is a better alternative? It may be dumb to ask but then can't all the functionality of DB2 be implemented in VSAMs itself one way or other?
Re: LDS VSAM and DB2.
Posted: Fri Jan 17, 2014 5:49 pm
by zprogrammer
Re: LDS VSAM and DB2.
Posted: Wed Jan 22, 2014 2:17 am
by dick scherrer
Code: Select all
can't all the functionality of DB2 be implemented in VSAMs itself one way or other?
Not by a developer - No.
The biggest difference to a coder is that DB2 is all about SQL and VSAM is not.
Re: LDS VSAM and DB2.
Posted: Wed Jan 22, 2014 12:38 pm
by Atif Alam
Thanks Pandora, this give a more info:
Basically, a file management system is that component of the overall system that manages stored files. Loosely speaking, therefore, it is "closer to the disk" than the DBMS is. In fact, the DBMS is typically built on top of some kind of file manager. Thus, the user of a file management systems will be able to create and destroy stored files and perform simple retrieval and update operations on stored records in such files.
In contrast to the DBMS, file managers:
•are not aware of the internal structure of the stored records, and hence cannot handle requests that rely on a knowledge of that structure (such as "find all employees with salary less than $50,000").
•provide little or no support for security and integrity rules
•provide little or no support for recovery and concurrency controls
•have no true data dictionary concept
•provide much less data independence than the DBMS does
But I was just thiking what prompted them to have DB2 rather than improving VSAMs itself.
Re: LDS VSAM and DB2.
Posted: Wed Jan 22, 2014 12:40 pm
by Atif Alam
Thanks Dick.
I think it's like as UNIX is written in C and has it's own advantages; similarly DB2 has over VSAM...
Re: LDS VSAM and DB2.
Posted: Tue Jan 28, 2014 1:53 am
by dick scherrer
I think it's like as UNIX is written in C and has it's own advantages; similarly DB2 has over VSAM...
The UNIX user or an admin may all be writting in C, but there is underlying code (kernel) that is written in the assembler language of the hardware. At least is was years ago.
I don't see the comparison between one coding language and another versus DB2 & VSAM. DB2 is a Database Management Syatem while VSAM is just another access method.