| SPD Engine Data Set Options |
Specifies the number of bytes to add to compressed blocks in a
data set opened for OUTPUT or UPDATE.
- n
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is the number of bytes to add.
Compressed SPD Engine data sets occupy blocks of space
on the disk. The size of a block is derived from the IOBLOCKSIZE= data set
option specified when the data set is created. When the data set is updated,
a new block fragment might need to be created to hold the update. More updates
might then create new fragments, which, in turn, increases the number of I/O
operations needed to read a data set.
By increasing the block padding in certain situations where many updates
to the data set are expected, fragmentation can be kept to a minimum. However,
adding padding can waste space if you do not update the data set.
You must weigh the cost of padding all compression blocks against the
cost of possible fragmentation of some compression blocks.
Specifying the PADCOMPRESS= data set option when you create or update
a data set adds space to all of the blocks as they are written back to the
disk. The PADCOMPRESS= setting is not retained in the data set's metadata.
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