This document discusses special topics for ERP software development in ABAP, including authorizations, locking objects, logical units of work, and updaters. Authorizations must be checked before programs access data. Locking objects prevent simultaneous changes to shared data. Logical units of work ensure data integrity by buffering database updates and only committing them when a transaction is complete. Updaters process the buffered updates and write them to the database.

1. ABAP Course
Chapter 6 – Specialities for ERP software
Lecturer: André Bögelsack, UCC Technische Universität München
Author: Valentin Nicolescu, André Bögelsack
ABAP Course André Bögelsack, Valentin Nicolescu 1

2. Copyright 2008 UCC TU München
All rights reserved
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3. Agenda
1. Authorizations
2. Lock objects
3. Logical units of work
4. Updater
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4. Authorizations
• Before starting a program user authorizations should always be
checked
• But: authorizations are not checked by the system
• Every ABAP program has to check authorizations by itself
• Different authorization levels: READ (01), CHANGE (02), DELETE
(03) for every data set
• Transaction: SU03
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5. Locking concept
• What happens when several users want to work on the same
data set?  data inconsistency
• Lock objects prevent simultaneous changes on data set
• Beside the lock concept of the database, SAP implements its own
lock concept
• SAP does not use the database’s lock concept
• Deadlock:
– May occur when two programs wait for each other to lock data
set
– Rare
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6. Locking concept
Modes:
1. Read lock = shared lock
• Locks data set for reading
• Several shared locks may exist on one data set at the same
time
• Prevents the SAP system from creating an exclusive lock on a
data set
2. Write lock = exclusive lock
• Locks data set for writing/changing
• No shared locks, only one is allowed at the same time
• First come, first serve
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7. Locking concept
Creation of a lock object:
• Creation can be done in data
dictionary (SE11)
• One lock object per database
table
• Lock objects are generated
automatically by using the
primary key
• There is only one lock object
dealing with all lock modes
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8. Usage of lock objects
• Two function modules are generated automatically when creating
a lock object:
– Enqueue_<lock object>  lock data set
– Dequeue_<lock object>  unlock data set
• Before writing/reading data set  lock data set
• After writing/reading data set  unlock data set
• In case of an error  unlock data set
• Use button ‘PATTERN’ to avoid misspellings
• Locks can be viewed and deleted in transaction SM12
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9. Generation of lock objects
Lock object
EZ_SPFLI
Activate
Function Function
ENQUEUE_ESFLIGHT DEQUEUE_ESFLIGHT
 Lock data set  Unlock data set
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10. ENQUEUE parameter‘s
Parameter Value Meaning
mode_<tabname> ‘S‘ Read lock (shared)
‘X‘ Exclusive lock (not shared)
<lock parameter> <value> Field values used to lock the data set
_wait SPACE If foreign lock, no new attempt
‘X‘ If foreign lock, new attempt
_collect SPACE Lock without local lock container
‘X’ Lock with local lock container
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11. Logical unit of work (LUW)
Logical unit of work (transaction)
breakdown
Process before
Process after
output (PBO)
input (PAI) 100 Commit
100
Dynpro
100
User input
Process before
Process after
output (PBO)
input (PAI) 200
200
Dynpro
Scenario: 200
What happens if a breakdown of the
SAP system occurs in the middle of the User input
transaction? What happens to the data?
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12. Logical unit of work (LUW)
• Problem:
– New data sets are transferred into the database by each screen
– Only if last screen of the program is reached and all data sets
are written to the database the data are correct
• Solution
– Updates to database are written to the updater process
– Only when last screen of the program is reached, the updater
receives a trigger to write data to database (commit) or to
dismiss (rollback)
 ensures data integrity
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13. Logical unit of work (LUW)
• Schema: Protocoll table
Data
Data
Data
Data Data
deletes
1 3
Work process Work process
2 5
Program Updater
4
 Lock data set
Database
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