Indexed Sequential Access Method

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Indexed Sequential Access Method

(ISAM) An IBM file management system allowing records to be accessed either sequentially (in the order they were entered) or via an index. Each index orders the records on a different key.

ISAM was followed by VSAM (Virtual Storage Access Method) and pre-dated relational databases.
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(Indexed Sequential Access Method) A common disk access method that stores data sequentially, while maintaining an index of key fields to all the records in the file for direct access. The sequential order would be the one most commonly used for batch processing and printing (account number, name, etc.).
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