DB2 uses a multithreaded architecture with processes and execution demand units (EDUs) to improve performance. The DB2 process model includes client programs, communication listeners that clients first contact, three types of agents (idle, coordinator, sub-agents) that are managed in an agent pool, and important database EDUs like prefetchers and page cleaners. Key configuration parameters related to the process model include the number of agents in the pool, number of coordinating agents, and number of I/O cleaners and servers per database.

1. SECTION – 3
DB2 ARCHITECTURE
DB2 Process ModelLecture 5

2. Contents
 Understanding Processes & Threads
 Multithreaded Architecture in DB2
 DB2 Process Model – The Big Picture
 Client Programs & Listeners
 DB2 EDUs/Agents & Agent Pool
 Important Database EDUs
 Related DBM & DB CFG parameters
 Summary

3. Understanding Processes &
Threads3
 A process is an executing instance of an application. It
can contain multiple threads. A thread could be
considered as a light-weight version of a process
 Thus, the essential difference between a thread and a
process is the work that each one is used to accomplish.
Threads are used for small tasks, whereas processes
are used for more ‘heavyweight’ tasks – basically the
execution of applications.

4. Multithreaded Architecture in
DB24
There are many advantages to using a multithreaded
architecture
for DB2 data server:
- A new thread requires less memory and fewer operating
system resources than a process
- The context switch time for threads is less than that for
processes

5. DB2 Process Model - The Big
Picture5
Listing All
EDUS
db2pd -edus

6. Client Programs & Listeners
 Client programs can be
remote or local, running on
the same machine as the
database server. Client
programs make first contact
with a database through a
communication listener.
 Communication listeners start
when the DB2 database server
starts. There is a listener for each
configured communication
protocol
 db2ipccm (IPC – local clients)
 db2tcpcm (tcpip – remote
clients)
 db2npcm (npipe protocol -
6
Client Programs Communication Listeners

7. EDUs / Agents
7
An agent can be thought of as a 'worker' that performs all
Database operations on behalf of an application. There are
three
types of DB2 agents:
 Idle agents – db2agent (idle)
 Active Coordinator Agent - db2agent (db_name)
 Subagent - db2agntp

8. Database EDUs
8
The following list includes some of the important EDUs that
are used
by each database:
 db2dlock : for deadlock detections
 db2loggw : log file writer
 db2pfchr : buffer pool prefetchers
 db2pclnr : buffer pool page cleaners

9. Database Server threads and
processes
9
 The system controller (db2sysc on UNIX
and db2syscs.exe on Windows operating systems) must
exist if the database server is to function.
 db2sysc, the main system controller EDU; it handles critical
DB2 server events
 db2licc, manages installed DB2 licenses

10. Related DBM & DB CFG parameters
10
 DBM CFG
 NUM_POOLAGENTS : Agent pool size (max)
 NUM_INITAGENTS : Initial number of agents in pool
 MAX_CONNECTIONS: maximum number of application connections
 MAX_COORDAGENTS : Max number of coordinating agents
 DB CFG
 NUM_IOCLEANERS : The number of page cleaners per database
 NUM_IOSERVERS : The number of prefetchers per database

11. Summary
11
 DB2 has a multithreaded architecture (Processes & EDUs)
 Process Model (db2pd –edus)
 Listeners (db2tcpcm & db2ipccm)
 3 types of agents (idle, coordinator agents, sub-agents)
 Agent Pool
 Database EDUs (prefetchers, page cleaners, log readers/writers etc)
 db2syscs.exe
 DBM & DB cfg related parameters

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