Oracle7 Server Administrator's Guide
Estimating Space Required by Hash Clusters
As with index clusters, it is important to estimate the storage required for the data in a hash cluster. Use the procedure described in "Estimating Space Required by Clusters" ![[*]](jump.gif)
, with the following additional notes:
- A sub-goal of the procedure is to determine the SIZE of each cluster key. However, for hash clusters, the corresponding sub-goal is to determine the SIZE of each hash key. Therefore, you must consider not only the number of rows per cluster key value, but also the distribution of cluster keys over the hash keys in the cluster.
- In Step 3, make sure to include the space required by the cluster key value. Unlike an index cluster, the cluster key value is stored with each row placed in a hash cluster.
- In Step 5, you are calculating the average hash key size, not cluster key size. Therefore, take into account how many cluster keys map to each hash value. Also, disregard the addition of the space required by the cluster key value, Ck. This value has already been accounted for in Step 3 (see previous item).