# How do you calculate block size from record length?

## How do you calculate block size from record length?

The values you set depend on whether the data sets are fixed length or variable length. For fixed-length records ( RECFM=F or RECFM=FB ), LRECL is the logical record length; and BLKSIZE equals LRECL multiplied by n where n is equal to the blocking factor.

## How many blocks are in a cylinder?

b) How many blocks are required to store the entire file? If the file is arranged sequentially (according to the ‘next block concept’) on disk, how many cylinders are needed? 1,000,000/20=50,000 blocks are required to store the entire file. A track has 25 blocks, a cylinder has 25*10=250 blocks.

What is block size in operating system?

Blocks can be of different sizes. The size of the block is known as the block size. Every file in OS occupies at least one block even if it is of 0 bytes. Block provides a level of abstraction for hardware that is responsible for storing and retrieving the data.

### What is disp old in JCL?

DISP parameter describes the status of the dataset. If the system obtains unit and volume information for an OLD, MOD, or SHR status, the data set is treated as if it exists or not physically on the device. One of two methods can be used to request exclusive control: DISP=NEW, DISP=MOD, or DISP=OLD on a JCL request.

### How is block fill calculated?

To core fill 200mm blocks allow 0.8m3 of concrete per 100 blocks. To core fill 200mm ‘H’ blocks allow 0.84m3 of concrete per 100 blocks. To core fill 300mm blocks allow 1.1m3 of concrete per 100 blocks. To core fill 300mm ‘H’ blocks allow 1.32m3 of concrete per 100 blocks.

What is the difference between FB and VB?

​Fb files will have fixed length records in file where as VB files have different length records.

## What does BLKSIZE(0) mean?

If BLKSIZE (0) is specified, the system will determine the optimal block size based on the maximum record length ( LRECL) and the physical characteristics of the disk, or approximately half of a physical track. Half track blocking is optimal in that it reduces the amount of wasted storage on the disk.

## What is block size in MVS?

Block size (BLKSIZE) specifies the maximum length, in bytes, of a physical block of storage in MVS. If BLKSIZE (0) is specified, the system will determine the optimal block size based on the maximum record length (LRECL) and the physical characteristics of the disk, or approximately half of a physical track.

Should I use BLKSIZE=0 zero or let SMS do it for me?

Using blksize=0 zero or letting SMS do it seems a wise choice. You’ll be glad you did when you migrate to IBM’s latest and greatest. The system does the recalcs for you. You misunderstand, the BLKSIZE is often bigger than 27998 bytes and I don’t understand why (not only in my shop).

### What does bufno 30 and BLKSIZE=0 mean?

BUFNO=30 is typically a decent number and the memory increase usually doesn’t impact the program. blksize=0 does not mean the blocksize will be zero. It tells the system to determine what the best blocksize is and use that. After the job runs, the dataset will have a proper blocksize.