Fragment
Enhanced Definition
In mainframe computing, a fragment typically refers to a small, unusable or inefficiently used piece of storage or data space. This condition, known as **fragmentation**, arises when memory or disk space is repeatedly allocated and deallocated, leaving behind non-contiguous blocks that are too small to be useful for new allocations, or when data extents for a dataset are scattered across a storage volume.
Key Characteristics
-
- Internal vs. External: Internal fragmentation occurs when an allocated block of memory or disk space is larger than the actual data it holds, leaving unused space within the block. External fragmentation occurs when available free space is broken into many small, non-contiguous blocks.
- Performance Impact: Both types of fragmentation can degrade system performance by increasing I/O operations (for scattered data) or by preventing larger contiguous allocations, leading to increased paging or allocation failures.
- Dynamic Nature: Fragmentation is a dynamic process that evolves over time as resources are used and released, making it a continuous management challenge.
- Resource Specific: Can occur in various resources, including virtual storage (memory), DASD volumes, DB2 table spaces and indexes, VSAM datasets, and CICS dynamic storage areas (DS
Related Vendors
ASE
3 products