Database Dictionary
A database must have a database dictionary; this file has the database name with extension .fdd. It is created with ctdbCreateDatabase(), and must exist for the user to connect to the database. Each database dictionary maintains information about the tables associated with the database. When a database is connected to the session, it is considered “active”.
Database Dictionary Layout
Field
|
Type
|
Length
|
Description
|
TYPE
|
CT_INT4
|
4
|
Record type: 1-database 2-table 3-index
|
STATUS
|
CT_INT4
|
4
|
Record status: 0-status ok 1-reserved
|
NAME
|
CT_FSTRING
|
128
|
Name of database or table or index
|
LINK
|
CT_FSTRING
|
128
|
Name of table if record type is 3-index
|
LINKNBR
|
CT_INT4
|
4
|
Table UID if record type is 3-index
|
PATH
|
CT_FSTRING
|
256
|
Path of database dictionary, data or index
|
SUPEXT
|
CT_FSTRING
|
16
|
Super file extension (if super file is used)
|
DATEXT
|
CT_FSTRING
|
16
|
Data file extension (usually .DAT)
|
IDXEXT
|
CT_FSTRING
|
16
|
Index file extension (usually .IDX)
|
VERSION
|
CT_INT4
|
4
|
Record version: 0x00010000 (version 1.0)
|
COUNTER
|
CT_INT4
|
4
|
Deprecated.
|
UID
|
CT_INT4
|
4
|
UID for database or table or index
|
OWNER
|
CT_FSTRING
|
128
|
Name of owner - used by the c-treeACE SQL server
|
MIRROR_NAME
|
CT_FSTRING
|
128
|
Name of mirrored file.
|
MIRROR_PATH
|
CT_FSTRING
|
128
|
Path of mirrored file.
|
RESERVED
|
CT_ARRAY
|
3128
|
Reserved for future use
|
This information is included for general information on the database dictionary structure. c-treeDB has appropriate functions to retrieve any needed information from the database dictionary, such as the table UID or path.
A database dictionary file has several different record types:
- Table records (the field Type set to 2) holds information about a data file (table).
- Index records (the field Type set to 3) holds information about an index file.
- A special type four record which maintained the COUNTER field has been been deprecated as of c-treeACE V9.0.
|
