Relationship between block size and extent size

[TomBascom]

Since you have changed the subject I have started a new thread for you:

could u please say me

1) the relation between block size and records per block bcos

2) i got an information that there is no relation between block size and extent size,is it true Mr.tom?

3) i created a large database which extent size crosses some GB's.first i created it with block size 4096 and in large.st file, i gave records per block as 32 and while defining the application area,i gave one variable and one fixed extent for all the applications. now i copied the structure file of the large DB which i created already and i created another one .st file (say largedb.st)and created a database with 8192 block size and i added some extents to already existing application area of the new .st file(say largedb.st) using prostrct add dbname new .stfile and the extent i created is a variable one.(i didnt define size for the variable extents for both the database say large.st and largedb.st)

Already i defined one variable extent there and am adding a new variable extent to it and after adding , i gave the cmd prostrct list largedb(just for updation).In that i could observe that the new extent which i added was there (which is a variable one) and already existing variable extent becomes a fixed one but i could see the new extent size of that fixed one is 128 and the newly added variable extent size is 32.

( i know that if we are not mentioning variable extent size,initially it wil be defined as 32 since its a default value but

why such variations(how 128 comes in it)? how the extent size has to be defined..based on records pr block or based on block size?

Block size & record records per block influence lots of things.

Extent size is a function of how much data is in the extent and how well packed the blocks are. Extent size is either fixed or variable. If it is fixed then it is whatever size it is. If it is variable then it will grow as data is added to it. How fast it grows depends on the relationship between block size, rows per block, blocks per cluster and average record size.

Progress extends a variable extent in multiples of the block size. That's probably why you see two different variable extent sizes.

Your specific example is difficult to diagnose. It would help to see the two .st files and the detailed directory listing showing how big the extents are from the OS point of view.

 

[richieasir]

hi all,
is there any limit for defining the extent size ie)it should be equal to 2gb or less for linux server?if it is why?

 

[TomBascom]

If you have enabled large files and your OS and the filesystem that the extents are on support it then there is no 2GB limit on extent sizes.

If in doubt, or if you think you may need to transfer the files to a system where the above conditions are not true then stick with 2GB or less.

Personally I often work on systems where there is no limit and I'm pretty comfortable with much larger extent sizes. It has been a while since I've generally felt that a 2GB extent was a limit that I needed to worry about.