Database Definition - Location Modes

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Intro to IDMS
Margaret Sliming
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Introduction
This presentation will cover the basic
concepts of IDMS database structure, data
relationships and access methods.
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Agenda










Data Relationships
Database Architecture
Database Definition
Currency
COBOL Commands
Error Handling
Central Version
Culprit
SQL
Additional Information / Sources
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Data Relationships
TABLE RELATIONSHIPS
PAYROLL
Many-to-Many
STUDENT
ID
NAME
ADDR
ID
TCHR SSN
SALARY
One-to-One
TEACHER
COURSE
STUD-CRSE
ID
NAME
SSN
DEPT ID
ID
NAME
TCHR ID
STUD ID
CRSE ID
One-to-Many
DEPARTMENT
ID
NAME
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Data Relationships (Con’t)

Data relates in three ways:




One-to-One (eg. Payroll & Teacher)
One-to-Many (eg. Teacher & Course)
Many-to-Many (eg. Course & Student)
Relational databases use foreign keys to relate
records and IDMS uses sets.
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Database Architecture
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Database Architecture

The preceding page illustrates how records are
stored in IDMS.

The database is comprised of areas which are
mapped to disk files. Areas are broken up into
pages which contain the database records. The
records are uniquely identified by the page
number, they reside on, and a sequence number,
called a line number. This makes up what is
known as the database key or DB-KEY.
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Database Architecture
Database Page
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Database Architecture
DATABASE KEYS
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Database Definition
PAYROLL-100
100 F
CALC
100-PYRL-ID DN
ADMIN-AREA
TEACHER-PAYROLL
TEACHER-200
200 F
CALC
200-TCHR-ID DN
FACULTY-AREA
TEACHER
-COURSE
COURSE-400
400 F
CALC
400-CRSE-ID DN
ACADEMIC-AREA
COURSE-STUDCRSE
DEPT-TEACHER
DEPT-300
300 F
CALC
300-DEPT-ID DN
FACULTY-AREA
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STUDENT-500
500 F
CALC
500-STUD-ID DN
ADMIN-AREA
STUDENT-STUDCRSE
STUD-CRSE-600
600 F
VIA
CRSE-STUDCRSE DN
ACADEMIC-AREA
10
Database Definition
Record Descriptions
01
01
01
PAYROLL-100.
01
COURSE-400.
05
100-PYRL-ID
PIC X(9).
05
400-CRSE-ID
PIC X(3).
05
100-PYRL-SSN
PIC 9(9).
05
400-CRSE-TITLE
PIC X(20).
05
100-PYRL-SALARY
PIC 9(6)V9(2).
05
400-CRSE-TCHR
PIC X(5).
TEACHER-200.
01
STUDENT-500.
05
200-TCHR-ID
PIC X(4).
05
500-STUD-ID
PIC X(4).
05
200-TCHR-SSN
PIC 9(9).
05
500-STUD-NAME
PIC X(30).
05
200-TCHR-NAME
PIC X(30).
05
500-STUD-ADDR
PIC X(40).
05
200-TCHR-DEPT
PIC X(4).
DEPT-300.
01
STUD-CRSE-600.
05
300-DEPT-ID
PIC X(4).
05
600-STUD-ID
PIC X(4).
05
300-DEPT-NAME
PIC X(15).
05
600-CRSE-ID
PIC X(3).
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Database Definition



A Schema contains the record, set and area
definitions for an IDMS database.
A Subschema contains the records, sets and
areas that can be referenced by an application
and whether they can be updated or retrieved
only.
A DMCL maps the database areas to file
blocks.
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Database Definition



To program IDMS applications, our most
valuable tool is the schema definition and/or
diagram, seen on slide 10, known as the
“Bachman” diagram.
In order to retrieve and/or update information
in the database, we have to know how to get to
it.
The following pages will detail how we define
data relationships in IDMS.
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Database Definition





Record Attributes
Location Modes
Set Attributes
Indexed Sets
Area Sweeps
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Database Definition - Record Attributes
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Database Definition - Record Attributes

Record ID: Unique numeric value within the
schema assigned to the record. It’s helpful to
include this number in the record name and to also
prefix each record element with it.

Storage Mode: This means storing the record as
fixed or variable. Fixed is the most desirable so the
record does not change size when it gets updated.
Variable records can get fragmented and thus take
more I/O to retrieve.
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Database Definition - Record Attributes

Record Length: This value includes the total length
of all data elements plus four bytes for each pointer
database key associated with the record. Pointers will
be discussed later with set options.

Location Mode, Set Name and Duplicates
Indicator will we discussed in more detail later in this
section.

Area Name: Name of the database area the record is
stored in.
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Database Definitiion - Location Modes

The manner in which a record occurrence is physically
located in an area of the database. The three types are:
CALC, VIA and DIRECT.

CALC: A method of determining the target page for
storage of a record in the database. The target page is
calculated is calculated by means of a randomizing
routine executed against the value of the Calc key in the
record.
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Database Definition - Location Modes

VIA: Clusters member records in the same physical
location for efficient database access. Optionally, Via
can cluster member records with their owners.

DIRECT: Populates an area in the order the records
are loaded. This mode is best used for data which is
static and will be retrieved in the order it physically
resides in the database.
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Database Definition - Location Modes
Example – CALC mode
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Database Definition - Location Modes
Example – VIA mode
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Database Definition – Location Modes
This example illustrates how records are stored VIA when the owner
and member reside in different areas.
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Database Definition - Location Modes
Example – DIRECT mode
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Database Definition - Set Attributes

Sets relate records to each other in IDMS using a
number of parameters.




Pointers: Next, Prior, Owner, Index, Index Owner
Membership: Mandatory Automatic, Mandatory
Manual, Optional Automatic, Optional Manual
Order (Unsorted sets): First, Last, Next, Prior
(Sorted sets): Ascending or
descending by key
A database record contains a pointer (aka Db-key)
for each record it relates to. ie. If it is stored Next,
Prior and Owner in a set, it will contain the pointer
for the owner, previous and next record in the set.
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Database Definition – Indexed Sets
SYSTEM-OWNED INDEX
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Database Definition – Indexed Sets
USER-OWNED INDEX
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Database Definition – Area Sweeps



This method of retrieval is used when records cannot
be retrieved using key information. The entire area is
read from beginning to end and the program selects the
desired records.
This can be a good method when all occurrences of a
record type are needed and there are not too many
different record types in the area.
The programmer must pay close attention to currency
when retrieving owner records with an area sweep and
then getting their member records when both records
reside in the same area. Looping can occur if the
owner record is not made current of area before each
obtain.
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Currency



IDMS keeps track of record occurrences,
being processed, by area, set, record type and
run-unit (program).
The current record is usually the last
record retrieved or updated.
Currency is extremely important to
understand, especially when updating a
database, for maintaining data integrity.
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COBOL Commands












ACCEPT
BIND
COMMIT
CONNECT
DISCONNECT
ERASE
FIND/OBTAIN
FINISH
IF
MODIFY
READY
ROLLBACK
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COBOL Commands - ACCEPT


Retrieves information pertaining to the status of the
database.
Format:
ACCEPT {TASK CODE } INTO return-location.
{TASK ID
}
{LTERM ID }
{PTERM ID }
{SYSVERSION}
{USER ID
}
{SCREENSIZE}
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COBOL commands - BIND


Initiates a run-unit and establishes addressability
in variable storage to the IDMS communication
block, record types and optionally to procedure
control information.
Format:
BIND {RUN-UNIT } .
{record-name }
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COBOL Commands - COMMIT


Makes database updates permanent. Ie. If a
program abends without having issued any
‘COMMIT’s, all updates issued by the program
will be rolled back.
Format:
COMMIT {
}.
{ALL}
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COBOL Commands - CONNECT


Establishes a record occurrence as a member of
a set occurrence. The set must not be defined as
Mandatory Automatic.
Format:
CONNECT record-name TO set-name .
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COBOL Commands - DISCONNECT


Removes a member record occurrence from a
set but does not delete the record from the
database. This command is only valid for
records which are optional members of a set.
Format:
DISCONNECT record-name FROM set-name .
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COBOL Commands - ERASE


Deletes a record occurrence from the database
and optionally deletes records subordinate to it.
Format:
ERASE record-name {
} .
{ALL MEMBERS}
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COBOL Commands - FIND / OBTAIN

The FIND statement locates a record
occurrence in the database; the OBTAIN
statement locates a record and moves the data
associated with the record to the record buffers.
Because the FIND and OBTAIN command
statements have identical formats, they are
discussed together. The six formats of the
FIND/OBTAIN statement are as follows:
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COBOL Commands - FIND / OBTAIN






FIND/OBTAIN CALC accesses a record occurrence by using
its CALC key value.
FIND/OBTAIN CURRENT accesses a record occurrence by
using established currencies.
FIND/OBTAIN DB-KEY accesses a record occurrence by
using its database key.
FIND/OBTAIN OWNER accesses the owner record of a set
occurrence.
FIND/OBTAIN WITHIN SET USING SORT KEY
accesses a record occurrence in a sorted set by using its sort key
value.
FIND/OBTAIN WITHIN SET/AREA accesses a record
occurrence based on its logical location within a set or on its
physical location within an area.
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COBOL Commands - FIND / OBTAIN
Formats:






FIND / OBTAIN CALC record-name .
FIND / OBTAIN CURRENT { record-name
}.
{WITHIN set-name }
{WITHIN area-name }
FIND / OBTAIN DB-KEY IS db-key .
FIND / OBTAIN OWNER WITHIN set-name .
FIND / OBTAIN record-name WITHIN set-name USING sort-key.
FIND / OBTAIN {NEXT} {
} WITHIN { set-name } .
{PRIOR} {record-name }
{ area-name }
{FIRST}
{LAST}
{seq-nbr}
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COBOL Commands - FINISH


Causes affected database sessions to terminate.
Format:
FINISH .
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COBOL Commands - IF


The IF statement allows the program to test for the
presence of member record occurrences in a set and to
determine the membership status of a record
occurrence in a specified set; once the set has been
evaluated, the IF statement specifies further action
based on the outcome of the evaluation. For example,
an IF statement might be used to determine whether a
set occurrence is empty and, if it is empty, to erase the
owner record.
Note: DML IF statements cannot be nested within
COBOL IF statements.
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COBOL Commands - IF

Depending on its format, the IF statement uses set or run-unit
currency. The object set occurrence of an IF statement is
determined by the owner of the current record of the named set;
the object record occurrence is determined by the current of run
unit.

Each IF statement contains a conditional phrase and an
imperative statement. When an IF is issued, the
precompiler first generates a call to the DBMS to
execute the conditional phrase; the results of the test
determine whether or not the imperative statement is
executed.
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COBOL Commands - IF
Formats:
 IF set-name EMPTY imperative-statement .

IF set-name NOT EMPTY imperative-statement .
IF set-name MEMBER imperative-statement .

IF NOT set-name MEMBER imperative-statement .

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COBOL Commands - Modify


Replaces the contents of a database record occurrence
with the values in it’s corresponding variable storage.
Note: The database record being modified, must
always be current of run-unit.
Format:
MODIFY record-name .
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COBOL Commands - READY

Prepares a database area for access by DML functions
and specifies that area's usage mode.

Format:
READY {
} USAGE-MODE {UPDATE } .
{ area-name }
{RETRIEVAL}
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COBOL Commands - ROLLBACK



Rolls back uncommitted changes made to the database
through an individual run unit.
Format:
ROLLBACK { CONTINUE } .
The CONTINUE option allows the run-unit to remain
active after the changes have been backed out.
Database access can be resumed without issuing BIND
and READY statements.
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ERROR HANDLING



After each IDMS command executes, a value is
returned into a field called ERROR-STATUS which is
‘0000’ if the command was successful, or a 4-byte value
indicating the command in error and the reason for the
error. The first two bytes of ERROR-STATUS
indicate the command and the last two bytes indicate
the cause of the error.
Every IDMS error should be trapped and the
appropriate action should be taken. This action may be
an error message or an Abort of the program
depending on the severity of the error.
A list of these error status codes can be found in
Volume 4, Chapter 11 of the ‘IDMS Messages and
Codes’ manuals.
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ERROR HANDLING
Component Major code DML function


















00 Any DML function
01 FINISH
02 ERASE
03 FIND/OBTAIN
05 GET
06 KEEP
07 CONNECT
08 MODIFY
09 READY
11 DISCONNECT
12 STORE
14 BIND
15 ACCEPT
16 IF
17 RETURN
18 COMMIT
19 ROLLBACK
20 LRF requests
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Central Version / Local Mode

CENTRAL VERSION is an IDMS system that enables
multiple applications to access the database concurrently. A
central version controls access to data at the individual record
(or row) level thus providing integrity while maximizing
concurrency. It also provides automatic recovery in the event of
failure. All applications executing within a TP monitor
(including DC/UCF) use central version services to access
IDMS data. Batch applications can access data in central
version or local mode.

LOCAL MODE is a mode of operation in which a batch
program uses a dedicated copy DBMS to access the database.
In local mode, only one program can update the database at a
time. Updates in local mode are usually rare and only done
when it is faster to back of the database, run the update program
and restore in the event of an abend than running under Central
Version.
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Central Version / Local Mode
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Culprit
Advantage CA-Culprit is a batch utility that generates reports
from conventional and database files.
Data Input: As shown in the diagram on the following page,
Advantage CA-Culprit can extract data from several database
and conventional file structures. As many as 32 conventional
files can be read and processed in one Advantage CA-Culprit
run. Each run can generate up to 100 reports from the same
input data. Reports can be formatted as printed output, stored
tables, or written to cards, tape, or disk.
The diagram shows The Advantage CA-Culprit Data Access
and Transfer Network. Advantage CA-Culprit can extract data
from and write reports to several database and file structures.
Advantage CA-Culprit is fully integrated with other products,
such as Advantage CA-IDMS/DB, the Integrated Data
Dictionary (IDD), and CA-ICMS.
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Culprit
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Culprit
Sample program to list Service Office Address History for a Provider:
DATABASE DICTNAME=DICT05
IN DB SS=DPU001
PATHAA DPR-PROVSVOFC DPR-ADDRHIST
01OUT 132 1330 D PS(3375) DD=SYS036,36 LT=S
0151*010 339-BILL-PROV-ID-NBR
0151*020 339-SERVICE-OFC-NBR
0151*030 364-SERVICE-OFC-ADDR-GRP
0151*040 364-SVCOFC-STATUS-CODE
0151*050 364-SVCOFC-ADDR-EFFDATE-FULL
0151*060 364-SVCOFC-ADDR-ENDDATE-FULL
0151*070 364-SVCOFC-PROVL-DATE-TIME
017
IF 339-BILL-PROV-ID-NBR = 'B20000'
017
DROP
017010
TAKE
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SZ=6
SZ=2
SZ=79
SZ=1
SZ=8
SZ=8
SZ=14
010
52
Culprit
Output from Sample program:
B20000
B20000
B20000
B20000
B20000
B20000
B20000
B20000
B20000
B20000
B20000
B20000
B20000
B20000
B20000
B20000
B20000
B20000
B20000
B20000
B20000
B20000
B20000
B20000
52
52
52
52
56
47
30
54
55
55
50
48
5
5
5
53
53
1
1
1
1
1
46
51
4/13/2015
7117 DAWN VIEW CT
11432123N VIEW CT
11432123N VIEW CT
7117 DAWN VIEW CT
NEW ADDRESS
7505 SYLVAN VALLEY WAY
7117 NEW ADDRESS
75
TEST ADDRESSS
TEST ADDRESSS
785
12123
7117 DAWN VIEW CT
7117 DAWN VIEW CT
7505 SYLVAN VALLEY WAY
75
75
5555555555555ET
555 MAIN STREET
555 MAIN STREET
555 MAIN STREET
555 MAIN STREET
DD
7505 SYLVAN VALLEY WAY
SUITE 5225
SUITE
TT
X
PO BOX 5
X
CITRUS HEIGHTS
CITRUS HEIGHTS
CITRUS HEIGHTS
CITRUS HEIGHTS
DIAMOND SPRINGS
CITRUS HEIGHTS
CITRUS HEIGHTS
CH
CITY
CITY
CH
DH
CITRUS HEIGHTS
CITRUS HEIGHTS
CITRUS HEIGHTS
CH
CH
PLACERVILLE
PLACERVILLE
PLACERVILLE
PLACERVILLE
PLACERVILLE
CC
CITRUS HEIGHTS
M Sliming
CA956100000C20
CA956100000C20
CA956100000C20
CA956100000A20
CA956190000A20
CA956100000C20
CA956213501C20
CA956100000A20
CA956100000C20
CA956100000A20
CA956100000A20
CA956100000C20
CA956284011C20
CA956284011C20
CA956284011C20
CA956100000C20
CA956100000A20
CA956213501C20
CA956213501C20
CA956213501C20
CA956213501C20
CA956213501C20
CA956100000C20
CA956100000A20
C
C
C
A
A
C
C
A
C
A
A
C
C
C
C
C
A
C
C
C
C
C
C
A
20040910
20040901
20040901
20040828
20050801
20041001
20050829
20040901
20030901
20040901
20040701
20041002
20060316
20040901
20040828
20041001
20040401
20060314
20060308
20060207
20060205
20040830
20041001
20040828
20040910
20040910
20040910
20040910
20050830
20041005
20050829
20040907
20040830
20041026
20041005
20041005
20040910
20040907
20041005
20041005
20060315
20060216
20060207
20041207
20041005
20041005
20040910140146
20040910135446
20040910135041
20040910124434
20050826105313
20041005100933
20050829143219
20040907150639
20041026154158
20040923141317
20040830143345
20041005101456
20060328111055
20040907150441
20040907132818
20041005101533
20040901155604
20060315113330
20060309113516
20060207161221
20060206131043
20040901160019
20041005101738
20040831153728
53
Culprit
ADDITIONAL INFORMATION
G:\SYSGRP\IDMS R16 Manuals\IDMS Manuals – PDF\B01287-1E
TSO DATASETS:
 DLST.CULP.SOURCE
 DLST.CULP.JCL
 DLST.CULP.PROC
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SQL




With the SQL feature, non-SQL defined IDMS
databases can be accessed using SQL DML (IDMS
version of SQL). This is done by either using the
Online Command Facility (OCF) or the batch program
IDMSBCF.
An SQL schema is created which maps to that of the
non-SQL IDMS database.
Records defined in the non-SQL schema can then be
accessed as tables in SQL.
The following page show an example of executing a
SELECT statement using OCF.
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SQL
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Additional Information / Sources

List of manuals and file names located on G:
drive at: G:\SYSGRP\IDMS R16 Manuals
Glossary:
 DML Reference – COBOL:
 Messages and Codes – Volume 4:
 SQL Option Self-Training Guide



B01251-1E
B01247-1E
B01259-2E
B01274-1E
G:\SYSGRP\2006 IUA Workshop
CDMMIS Schema Definition:
DLST.IDMS.RPTS(CV5SCHEM)
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