Database Administrator Guide > Database Administrator Guide > Calculating Disk Space > Space Requirements for Modify Operations > Summary of Space Requirements for Modify Operations
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Summary of Space Requirements for Modify Operations
The following table provides a summary for estimating disk space requirements.
In the table, “O+N” (Original+New tables) corresponds roughly to twice the table size (2X) and “O+N+S” to three times the table size (3X). The space required can be affected by whether an index is added (“I” in the table) or existing index space freed (“U” in the table).
Original Table Structure
Modified to
 
 
 
Heap
Hash
ISAM
B-tree
Heap
O+N
O+N+S
O+N+S+I
O+N+S+I
Hash
O+N
O+N+S
O+N+S+I
O+N+S+I
ISAM
O+N-U
O+N+S-U
O+N+S
O+N+S
B-tree
O+N-U
O+N+S-U
O+N+S
O+N+S
Legend:
O = Original table size
N = New table size
S = A sort is required
I = Index is being added
U = Space freed because an index is no longer necessary
Note:  Remember that numerous factors contribute to the actual disk space used in a particular modify operation. Additional factors include compression and the various fill values.
Last modified date: 11/09/2022