Fujitsu UDS/SQL V2.5 Manual Do Utilizador
U929-J-Z125-9-76
197
D
ok
us
c
h
abl
on
en
1
9x
24 V
e
rs
ion
7
.3
us
f
ü
r F
ram
eM
ak
er
V
7
.x
v
o
m
1
4.
02
.2
00
7
©
c
o
gni
tas
Gm
b
H
20
01-
20
07
18
. Ok
tobe
r 20
07
S
ta
nd
1
1:
29
.5
0
P
fa
d:
G
:\
v
og
t\
fs
c
\ud
s
\M
anu
al
e
\e
n\
ud
s
e
nt
_e\
u
ds
ent
.k
0
7
7 Structure of pages
When creating a database using DDL and SSL, the user does not usually require infor-
mation on the structure of pages, records and tables.
The following two chapters are intended as a reference section for users interested in
special details.
mation on the structure of pages, records and tables.
The following two chapters are intended as a reference section for users interested in
special details.
The entire storage space provided for the data in a database is divided into realms. Every
realm consists of a specific number of pages that is specified when creating the database.
This number may be subsequently modified (see the "
realm consists of a specific number of pages that is specified when creating the database.
This number may be subsequently modified (see the "
" manual).
The length of a page may be 2048, 4000 or 8096 bytes and must be uniform within a
database. This page length is defined when creating the database with the BCREATE utility
routine and can be subsequently extended with BPGSIZE (see the "
database. This page length is defined when creating the database with the BCREATE utility
routine and can be subsequently extended with BPGSIZE (see the "
" manual for details).
Pages with a length of 4000 or 8096 bytes are each embedded in a page container, which
consists of a 64-byte header that precedes the page itself, and a 32-byte trailer at the end.
consists of a 64-byte header that precedes the page itself, and a 32-byte trailer at the end.
The following types of pages can be distinguished in the structure of a realm. These pages
differ in their data contents and structure:
differ in their data contents and structure:
Act-key-0 page
contains realm-specific data; is always the first page in a realm
Act-Key-N page
contains realm-specific data; is always the last page in a realm
FPA page
serves free place administration (FPA) on realm level. At least one FPA page is
always present.
always present.
DBTT anchor page
manages the DBTT areas of a record type (DBTT: Database Key Translation Table).
DBTT page
page of a DBTT area. Manages the records of a record type.
CALC page
contains a hash area
Data page
contains records which are not stored in a hash area, and tables (except DBTT)