005 Important Parameters used while creating a VSAM file

[music] Welcome everyone. In this section we will understand about all the important parameters which are used for VSM files. So the first one is name. Name is a keyword which is used to specify the name of VSAM cluster or alternate index. The next one we have is record size. It is called as recz. So record size parameter has two values which are average record length and then maximum record length. So the syntax for this is rec SZ and then you have to give average record length and space and after that we have to give the maximum record length. Right? So the average specifies the average length of logical records in the file and maximum denotes the maximum length of the record. Now how do you decide the average record length when we define a v sub file? There are a lot of factors actually there is no such rule about average record length or maximum record length. But you have to consider few factors. For example, maximum record length of each record or average record length after combining all the records. Now consider an example. You have six record of record lengths with suppose 80, 130, 55, 185, 80 and 200. Then what is the average record length? So you can calculate the average record length simply by 80 + 130 + 55 + 185 + 80 + 200 divided by 6. So if you sum up all these values and if you divide by the number six because it has six records then almost then you'll get a value close to 120 or 122 right. So you can give a value of 122 as your average record length. Similarly for maximum record length you can see that the maximum record length of one record was 200. So you can give maximum record length as 200. So please note that average record length must be less than or equal to maximum record length. VSM uses this figure for optimization purpose for a VM file. If both average record length and maximum record length are same that means the record size is fixed. Okay. So most important point to note here is the average record length must be less than or equal to maximum record length and it is not important to give an exact figure of average record length or maximum record length but you have to make sure that whatever value you are giving for maximum record length should be proper because that has more impact compared to if record length. Now the next one we have is control interval size. This is also called as CISZ right.