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What is ISAM and what is a Key-Value Store?

Indexed Sequential Access Method (ISAM) is a record-oriented database architecture that permits extremely fast access to data. ISAM data is organized into records stored in data files. Separate index files are used to store key-values (NoSQL) that identify each record, along with pointers that locate the corresponding record in the data file.

The index makes it possible to retrieve individual records quickly without having to search an entire data set.
For example, an accounts payable system using an ISAM database structure may define a vendor data file indexed by vendor name and vendor number, and an invoice data file indexed by vendor number and invoice number. In this case, each data file has two indexes. Although each data file is indexed by vendor number, there is a separate vendor number index for each data file.

A “key-value pair” is simply two pieces of information: (1) an identifier that will be used to uniquely find the pair and (2) a second piece of information: the value. Think of the key as a unique identifier and the value as a block of associated information. Going back to our accounts payable system above, consider this system vendor database:

Vendor Number

Vendor Name

Vendor Address


ACME Company

101 Main Street, St Louis, MO 65101


XYZ Corporation

102 main street, Kansas City, KS 64105

If one of the indexes is over Vendor Number, then the “key” is 1000 for the first record, and the remaining contents “ACME Company” and “101 Main Street, St Louis, MO 65101” make up the “value” component.

What’s the difference between ISAM and Key-Value?

If an ISAM database isn’t a key-value store, then I don’t know what a key-value store is!

— The thought many of our veteran developers have in this “new” age of NoSQL.

In practical terms, there isn’t any. You can think of a key-value store as a fundamental component in the implementation of an ISAM database. While “key-value” is more popular in the NoSQL space, there are many environments, such as COBOL, where the term “ISAM” (and it’s close parallel, “VSAM”) are still widely used. If this is you or your background, you can rest assured that our c‑treeACE key-value store has derived its roots from ISAM. Therefore, anywhere you see “key-value” on our web pages and literature, you can replace this with the term “ISAM” as you understand it.

What makes FairCom’s ISAM different?

The record-oriented ISAM database architecture has been around for many years, but unlike many of our competitors, FairCom has continuously evolved and improved the fundamental concepts. FairCom’s ISAM implementation has a rich API of over 250 function calls that empower the application developer to obtain precise control over their data access needs. This control, and the smaller code footprint of an ISAM implementation, provides opportunities for driving exceptional performance when compared to traditional relational systems by avoiding relational processing overhead.

When comparing c‑treeACE NoSQL to other NoSQL solutions, keep the following points in mind:

  • Over 30 years of proven reliability
  • Used by over 40% of the Fortune 100
  • Available ACID-compliant transaction support
  • Automatic system recovery, roll forward, roll back
  • Full SQL support available over your NoSQL Data
  • Wide array of available APIs / Frameworks
  • Fixed and variable-length record support
  • Cross-platform support
  • NoSQL user-defined functions and procedures
  • Batches, sets, ranges
  • Data and index filters
  • Partition file support
  • Automatic index tree pruning

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