Lesson 8 Companion — Custom Persistence Modeling

This companion expands Lesson 8 — Custom Persistence Modeling.

The teacher-led lesson intentionally stops after:

Domain
  ↓
Data Element
  ↓
Database Table
  ↓
Activation / Data Preview

No direct database writes are required today.

That split is deliberate so the afternoon Practice tests only persistence-modeling skills.

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1. Why this lesson exists before RAP

SAP's current RAP development flow begins with persistence and data modeling before behavior.

The course follows that logic:

Lesson 8
Persistence model

Lesson 9
Direct persistence mechanics

Lesson 10
RAP BO structure

Lesson 11
Managed behavior

Lesson 12
EML

Students first understand what the framework will sit on top of.

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2. Why define table is still taught

Current ABAP Cloud also supports:

define table entity

CDS Table Entities are an important newer persistence model.

However, current SAP learning content still explicitly teaches source-based ABAP Dictionary tables using:

define table

together with:

Domains
Data Elements
client fields
primary keys
table annotations

This remains useful certification knowledge.

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3. define table vs define table entity

High-level comparison:

	Source-based DDIC table	CDS Table Entity
Definition	define table	define table entity
Persistent	Yes	Yes
ABAP SQL source/target	Yes	Yes
Can be RAP active persistence	Yes	Yes
Domain/Data Element-centric teaching	Yes	Different CDS-native model
Hands-on in this course today	Yes	No

Do not try to learn both persistence models simultaneously in the first custom-table exercise.

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4. Dictionary DDL vs CDS DDL

These syntaxes look related but represent different object families.

define table ...

is source-based ABAP Dictionary DDL.

define view entity ...

is ABAP CDS DDL for a query/model entity.

define table entity ...

is ABAP CDS DDL for a persistent table entity.

The keyword tells you what kind of artifact you are creating.

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5. Row grain

A reliable database design begins with a sentence:

One row represents ...

Reservation:

One row represents one workshop reservation.

Support Issue Practice:

One row represents one support issue.

If the sentence is unclear, the key and field design are usually unclear too.

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6. Technical identity vs business identity

The course uses:

UUID

as technical identity.

It separately stores:

ReservationNo
IssueNo

as business-facing identifiers.

This avoids coupling persistence identity to future business numbering.

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7. UUID choice

The persistence key uses:

SYSUUID_X16

which represents a RAW(16) UUID.

This choice prepares the table for later managed RAP UUID numbering.

In Lesson 9, students will also generate a UUID directly in ABAP so they can understand the low-level mechanism.

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8. Domain role

A Domain defines technical characteristics such as:

type
length
decimal places
value range

Reservation Status:

ZDM_RSTAT_###
CHAR(1)
N/C/X

Support Issue Status:

ZDM_ISTAT_###
CHAR(1)
O/I/C

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9. Fixed-value nuance

Domain fixed values are valuable metadata.

They can support framework behavior and input assistance.

They should not be described as:

an unconditional database CHECK constraint that implements all business rules.

Future RAP behavior still needs validations for transactional rules.

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10. Data Element role

A Data Element connects technical typing with reusable business semantics.

It can provide:

Domain-based type
field labels
developer description
reusable field meaning

A Domain itself is not the business field type used in the table.

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11. SAP recommendation for business fields

SAP's current data-modeling learning material recommends Data Elements for business fields so semantic metadata and labels are reusable.

The course intentionally creates only one custom Data Element in the guided scenario to avoid spending most of the day creating near-identical repository objects.

Production modeling can go further.

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12. Client handling

The pattern:

key client : abap.clnt not null;

makes the normal application table client-dependent.

For standard ABAP SQL access, the current client is handled implicitly.

That is why later code will not normally write:

WHERE client = @sy-mandt

for every access.

Client handling is data isolation, not authorization.

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13. Primary-key order

For the course tables:

client
uuid

are the key fields and appear at the beginning of the field list.

This gives a client-dependent technical key.

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14. NOT NULL

NOT NULL prevents SQL NULL.

It does not mean:

not blank
not zero
business mandatory

For example:

CHAR(10) initial value

is still a value from the ABAP perspective.

Later RAP field characteristics and validations can model business-required fields.

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15. Table annotations reference

Guided table:

@EndUserText.label : 'Workshop Reservations'
@AbapCatalog.enhancement.category : #NOT_EXTENSIBLE
@AbapCatalog.tableCategory : #TRANSPARENT
@AbapCatalog.deliveryClass : #A
@AbapCatalog.dataMaintenance : #RESTRICTED

Key teaching points:

normal transparent table
application data
restricted generic maintenance
not extensible for this exercise

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16. Amount/currency semantics

Current SAP examples use a qualified field reference at table level:

@Semantics.amount.currencyCode : 'zresv_###.currency_code'
fee : abap.curr(10,2);

The Support Issue table uses the same pattern:

@Semantics.amount.currencyCode : 'zissue_###.currency_code'
estimated_cost : abap.curr(10,2);

This metadata matters because a numeric amount without its currency is incomplete business information.

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17. RAP reuse Data Elements

The table includes:

ABP_CREATION_USER
ABP_CREATION_TSTMPL
ABP_LOCINST_LASTCHANGE_USER
ABP_LOCINST_LASTCHANGE_TSTMPL
ABP_LASTCHANGE_TSTMPL

These are standard RAP-oriented reuse types.

Field names used in the course:

local_created_by
local_created_at
local_last_changed_by
local_last_changed_at
last_changed_at

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18. Local vs total last changed

Local

local_last_changed_at

will later support a local ETag.

Total

last_changed_at

will later matter for total-ETag/draft scenarios.

Keeping both now avoids a persistence redesign later.

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19. Full guided Domain reference

Create:

ZDM_RSTAT_###

Properties:

Type:   CHAR
Length: 1

Fixed values:

Value	Description
N	New
C	Confirmed
X	Cancelled

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20. Full guided Data Element reference

Create:

ZDE_RSTAT_###

Domain:

ZDM_RSTAT_###

Suggested labels:

Short:   Status
Medium:  Reservation Status
Long:    Reservation Status
Heading: Status

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21. Full guided table reference

@EndUserText.label : 'Workshop Reservations'
@AbapCatalog.enhancement.category : #NOT_EXTENSIBLE
@AbapCatalog.tableCategory : #TRANSPARENT
@AbapCatalog.deliveryClass : #A
@AbapCatalog.dataMaintenance : #RESTRICTED
define table zresv_### {

  key client                : abap.clnt not null;
  key uuid                  : sysuuid_x16 not null;

  reservation_no            : abap.numc(8) not null;
  customer_name             : abap.char(60) not null;
  customer_email            : abap.char(100);
  workshop_code             : abap.char(10) not null;
  reservation_date          : abap.dats not null;
  status                    : zde_rstat_### not null;

  @Semantics.amount.currencyCode : 'zresv_###.currency_code'
  fee                       : abap.curr(10,2);

  currency_code             : abap.cuky;
  notes                     : abap.char(255);

  local_created_by          : abp_creation_user;
  local_created_at          : abp_creation_tstmpl;
  local_last_changed_by     : abp_locinst_lastchange_user;
  local_last_changed_at     : abp_locinst_lastchange_tstmpl;
  last_changed_at           : abp_lastchange_tstmpl;

}

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22. Why the guided table uses built-in types

Examples:

customer_name  : abap.char(60);
workshop_code  : abap.char(10);

This is legal and keeps the first persistence exercise manageable.

Students should still know the production recommendation:

use reusable Data Elements where business semantics are reusable/valuable

The course deliberately demonstrates that pattern with Status.

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23. Data Preview

For a Database Table in ADT:

Alt + F8

or:

Open With → Data Preview

At the end of Lesson 8, zero rows is correct.

The important result is:

the table activates
its schema is correct

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24. Practice design-review exercise

The Practice begins with a deliberately weak design:

define table zissue_### {
  key issue_no      : abap.numc(8);
      status        : abap.char(1);
      estimated_cost: abap.curr(10,2);
      currency_code : abap.cuky;
}

Students should identify problems such as:

no client key
no technical UUID
business number used as technical key
status has no reusable Domain/Data Element
no amount/currency semantic relationship
no RAP administrative fields
no explicit NOT NULL decisions
missing normal table annotations

The purpose is not merely to "spot syntax errors."

It tests persistence design reasoning.

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25. Practice Domain reference

Create:

ZDM_ISTAT_###

Type:

CHAR(1)

Fixed values:

Value	Description
O	Open
I	In Progress
C	Closed

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26. Practice Data Element reference

Create:

ZDE_ISTAT_###

Domain:

ZDM_ISTAT_###

Suggested labels:

Short:   Status
Medium:  Issue Status
Long:    Support Issue Status
Heading: Status

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27. Full Practice table reference

@EndUserText.label : 'Support Issues'
@AbapCatalog.enhancement.category : #NOT_EXTENSIBLE
@AbapCatalog.tableCategory : #TRANSPARENT
@AbapCatalog.deliveryClass : #A
@AbapCatalog.dataMaintenance : #RESTRICTED
define table zissue_### {

  key client                : abap.clnt not null;
  key uuid                  : sysuuid_x16 not null;

  issue_no                  : abap.numc(8) not null;
  title                     : abap.char(80) not null;
  description               : abap.char(255);
  requester_email           : abap.char(100);
  priority                  : abap.char(1);
  status                    : zde_istat_### not null;
  reported_on               : abap.dats not null;

  @Semantics.amount.currencyCode : 'zissue_###.currency_code'
  estimated_cost            : abap.curr(10,2);

  currency_code             : abap.cuky;

  local_created_by          : abp_creation_user;
  local_created_at          : abp_creation_tstmpl;
  local_last_changed_by     : abp_locinst_lastchange_user;
  local_last_changed_at     : abp_locinst_lastchange_tstmpl;
  last_changed_at           : abp_lastchange_tstmpl;

}

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28. Why Priority is not another required Domain today

A second custom Domain/Data Element would be valid.

It is intentionally optional because the practice goal is:

prove you can reproduce the pattern independently

not:

maximize repository-object count

Students who finish early can model Priority as a reusable type in the optional challenge.

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29. Certification-style reasoning

Students should be able to explain without source code:

Domain vs Data Element
technical key vs business identifier
client handling vs authorization
SQL NULL vs ABAP initial
amount vs currency
local vs total last change
DDIC table vs CDS view

Those distinctions matter more than memorizing one table definition.

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30. Troubleshooting

Data Element cannot find Domain

Check:

Domain activated?
correct suffix?
correct package/object?

Table cannot find custom Data Element

Activate:

ZDM_...
ZDE_...

before activating the table.

Currency annotation error

Check the qualified reference:

zresv_###.currency_code

or:

zissue_###.currency_code

Table name rejected

Check the repository name length.

Data Preview shortcut does not work

Use:

Open With → Data Preview

instead.

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31. Current SAP references

Useful current SAP learning/help topics for this lesson:

Building Data Models with the ABAP Dictionary and ABAP Core Data Services
  → Creating Database Tables
  → Defining Domains and Data Elements

ABAP Cloud Help
  → Database Tables
  → RAP Reuse Data Elements
  → Creating/Enabling RAP Persistence

The course uses the same core patterns:

define table
client key
Data Elements
amount/currency references
RAP administrative fields