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Answer Posted / krishna
When there isn't enough space in the control interval VSAM performs a control interval split by moving some records to the free control intervals. If there isn't a free control interval, VSAM performs a control area split by allocating a new control area and moving half of the control intervals to it.
There are two types of splits used extensively in VSAM.
CI-SPLIT Movement of some records from an existing CI to another free CI in the same CA because a record add or update cannot be accommodated in the existing one.
A CI split requires a number of I/O operations and this degrades the performance of the VSAM file. The correct amount of the space will need to be allocated for the CI (internal percentage of free space allocation). This will result in two half-empty CI's instead of one full and one empty CI.
CA-SPLIT Movement of the half of the records in an existing CA to a new CA because a record add or update cannot be accommodated in the existing CA. This results in two approximately half-full CA's instead of one full and one empty CA. This is inefficient because it involves a high level of I/O operations.
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