Database Reference
In-Depth Information
RA
) in a given ordering determined by their compilation from the original host
source program
P
:
(
0
, In
R
,
1
)
Initial input, loads the physically stored database into data
(1, ACOM, 4)
memory and assigns
x
1
=
x
2
=
x
4
=
0 and
x
3
=
1
(
2
, Out
R
,
3
)
transfers a triple
(
0
,n,R)
in I/O memory to
M
U
,
n
is the
value of
x
2
(error),
R
=⊥
only for execution of
'SELECT...'
(3, RETURN, 4)
End of every program
(4, NOP,5)
(
5
, In
∗
ER
,
6
)
Waits for CALLs from
M
U
(given by
Out
R
(st(j))
,
where
st(j)
is the current state of
M
U
)
(
6
,t
1
,
4
,
10
)
...
(n,
0
,L)
is received from
M
U
and
x
2
=
0,
x
1
≥
1is
imposed
(
10, DEC, 11
)
(
11
,t
4
,
12
,
20
)
(12, VCON, 13)
COMMIT; checks the consistency of a database in memory
(
13
,t
2
,
14
,
2
)
(14, COM, 1)
extracts a database from working memory (Buffer) and
save a database in the physical storage
...
(20, DEC, 21)
(
21
,t
4
,
22
,
30
)
(22, RBACK, 1)
ROLLBACK
...
(30, DEC, 31)
(
31
,t
4
,
32
,
40
)
(
32
,P
1
,
2
)
Plan
P
3
...
...
(N
−
1
,
DEC
,N)
where
N
=
1
+
10
∗
n
(N,t
4
,N
+
1
,N
+
2
)
(N
+
1
,P
n
,
2
)
last Plan
P
n
,n
≥
4 in the Application Plan
(N
+
2
,
ERR
,
2
)
...
Program 2
DEC
)
k
,
k
Let us denote the parts of the Application Plan by
Ap
k
=
P
k
◦
(t
4
◦
=
1
,
2
,...,n
, where:
•
P
1
=
◦
◦
t
2
◦
ACOM
COM
VCON is the kernel for COMMIT;
•
P
2
=
ACOM
◦
RBACK is the kernel for ROLLBACK;
•
P
k
,k
=
3
,...,n
are the kernels for embedded SQL formulas (
P
k
are the arrows
in
RA
, composed of unary operators in
Σ
RA
).
