group Definition/General, tcl.group Verb: Access/TCL, group Definition/General

group

Command group Definition/General
Applicable release versions:
Category General (155)
Description partition in a file consisting of one or more linked frames used for storing and retrieving items.
When a file is created it is given a "modulo" which specifies how many one-frame groups are initially allocated for this file as the primary space. The group number is calculated by hashing the item-id with the modulo creating an integer "remainder" in the range zero to modulo minus one. The group number is added to the file's "base" giving the frame number of the group where the item is stored.
The hashed to group is sequentially searched to locate a specific item. By choosing the modulo appropriately items can usually be located in a single disk access regardless of the number of items in the file. Overflow frames are automatically linked to a group to expand its storage capacity dynamically. Also, these frames become released back to the overflow pool as the group contracts in size.
Syntax
Options
Example
Purpose
Related file
tcl.create-file
reallocation
modulo.def
hashing
linked.overflow
overflow.table
frame
tcl.group

tcl.group

Command tcl.group Verb: Access/TCL
Applicable release versions:
Category TCL (746)
Description displays summary information about each group in a file.

The items in the group are summarized showing:
a) fid of group in decimal,
b) offset to beginning of item in the group in hexadecimal,
c) size of item in hexadecimal,
d) item-id.
Syntax group file.reference {(options)}
Options i Displays only those groups that have not had any items changed since the last file restore.
n No pause; suppresses pause at the end of the page on terminal display.
p Directs output to system printer, via the Spooler.
s Suppresses listing of details; displays summary group statistics only.
Example
Purpose
Related file
tcl.item
group

group

Command group Definition/General
Applicable release versions:
Category General (155)
Description partition in a file consisting of one or more linked frames used for storing and retrieving items.
When a file is created it is given a "modulo" which specifies how many one-frame groups are initially allocated for this file as the primary space. The group number is calculated by hashing the item-id with the modulo creating an integer "remainder" in the range zero to modulo minus one. The group number is added to the file's "base" giving the frame number of the group where the item is stored.
The hashed to group is sequentially searched to locate a specific item. By choosing the modulo appropriately items can usually be located in a single disk access regardless of the number of items in the file. Overflow frames are automatically linked to a group to expand its storage capacity dynamically. Also, these frames become released back to the overflow pool as the group contracts in size.
Syntax
Options
Example
Purpose
Related file
tcl.create-file
reallocation
modulo.def
hashing
linked.overflow
overflow.table
frame
tcl.group