Dataset : size of data file change after orchadmin cp
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Dataset : size of data file change after orchadmin cp
Hi All,
I have an issue with orchadmin cp.
Some datasets are migrated from an old sever and copies were made with orchadmin cp.
eg.
export APT_CONFIG_FILE=4n.apt
orchadmin cp A.ds B.ds
where 4n.apt is used to generate A.ds
The record count for both files are same , however it was found that the size of data file in B.ds and A.ds are different. Roughly, the size of A.ds is double of B.ds
I have an issue with orchadmin cp.
Some datasets are migrated from an old sever and copies were made with orchadmin cp.
eg.
export APT_CONFIG_FILE=4n.apt
orchadmin cp A.ds B.ds
where 4n.apt is used to generate A.ds
The record count for both files are same , however it was found that the size of data file in B.ds and A.ds are different. Roughly, the size of A.ds is double of B.ds
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Why not look at the segment files (using the Data Set Management tool in Designer) to try to work out where the differences actually lie? In particular, review how many 32K or 128K blocks are involved for each Data Set.
Space in a Data Set includes any unused space in these storage blocks. It may be the case that the orchadmin cp command has been able to pack blocks more efficiently, particularly if A.ds has been appended to on occasions.
Appending to a Data Set does not re-use any internal storage blocks - it simply adds more blocks to the end of the segment file structure.
Space in a Data Set includes any unused space in these storage blocks. It may be the case that the orchadmin cp command has been able to pack blocks more efficiently, particularly if A.ds has been appended to on occasions.
Appending to a Data Set does not re-use any internal storage blocks - it simply adds more blocks to the end of the segment file structure.
IBM Software Services Group
Any contribution to this forum is my own opinion and does not necessarily reflect any position that IBM may hold.
Any contribution to this forum is my own opinion and does not necessarily reflect any position that IBM may hold.
What versions were the two servers? The copy might have changed the string column compression attribute in the Datasets.
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I wanted to check up at work, but forgot to do so. I do believe that the default representation for VarChar() fields in datasets went from uncompressed to compressed between 7.5.1 and 9.1.2, which would account for a smaller file at 9.1.2 despite having the same number of data records and identical contents.
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For what it's worth, the migration guide section for migrating data sets leads to this technote:
How to move dataset from one server to another in IBM InfoSphere DataStage
How to move dataset from one server to another in IBM InfoSphere DataStage
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