Chapter 9. GT.M Database Structure(GDS)

Revision History
Revision V6.0-003/1	19 February 2014	In “File Header Data Elements ”, updated the descriptions for V6.0-003.
Revision V6.0-003	27 January 2014	In “GDS Blocks ”, corrected the description of block header fields.
Revision V5.5-000/10	28 September 2012	In “Use of Keys ”, corrected the first sentence as follows: GT.M locates records by finding the first key in a block lexically greater than, or equal to, the current key. Added the “Using GDS records to hold spanning nodes ” section.
Revision V5.4-002B	24 October 2011	Conversion to documentation revision history reflecting GT.M releases with revision history for each chapter.

Contents

Database File Organization with GDS

Database File Header
File Header Data Elements
MLOCK Space

Local Bitmaps

Master Bitmap

Database Structure

Tree Organization
GDS Blocks
GDS Records
GDS Keys
Compression Count
Use of Keys
Characteristics of Keys
Global Variable Names
String Subscripts
Numeric Subscripts

GDS is an FIS proprietary internal database structure used to store global variables and lock resource names. A high-level understanding of GDS can help database administrators correctly interpret GT.M logs/error messages, and maintain database metrics. You should always consult GT.M support (gtmsupport@fisglobal.com) in the unlikely event of getting database integrity issues.

	Note
	This chapter provides a high-level overview of GDS components. A comprehensive description of all the components of GDS is beyond the scope of this chapter.

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