Db2 address spaces involved in distributed data processing

With data sharing, as you increase throughput by spreading work across more systems, you can expect some processing increases. These increases are caused by the cost of managing and controlling locks, buffers, and data sets. However, these increases are limited to the percentage of your workload that is accessing data with inter-Db2 read/write interest.

The z/OS® address spaces that are involved in distributed database processing with Db2 for z/OS and the purpose of each address space is as follows, where ssnm is the name of the Db2 subsystem.
Database services address space (ssnmDBM1)

The database services address space is responsible for accessing relational databases that are controlled by Db2 for z/OS and provides most database-related services. The input and output to database resources is performed on behalf of SQL application programs in this address space.

Activities that occur in this address space include prefetching, space management, and deferred write. With Db2 data sharing, the following activities occur under SRBs in this address space:

  • Castouts
  • Prefetch interactions with the coupling facility
  • P-lock negotiation
  • Updates to SYSLGRNX
  • Group buffer pool checkpoints
System services address space (ssnmMSTR)

The system services address space starts and stops Db2, and controls local access to Db2 for z/OS, and performs various system-related functions.

Activities that occur in this address space include commit processing after updates, inserts, and deletes; logging; backout processing; and archiving. With Db2 data sharing, writes to the group buffer pool and the global unlocking that occurs during commit processing both occur under service request blocks (SRBs) in this address space.

Distributed data facility (DDF) services address space (ssnmDIST)

The distributed data facility (DDF) services address space (often called the DDF address space) supports network communications with other remote systems and execution of database access requests on behalf of remote users to support distributed database services.

When a distributed database request is received, DDF passes the request to the database services address space (ssnmDBM1), so that the required database I/O operations can be performed.

Internal resource lock manager (IRLM) address space (irlmproc)
Db2 uses the IRLM address space to control access to database resources and locking.

Activities that occur in this address space include global lock conflict resolution. When a system is running normally, SRB for the irlmproc address space time is substantially lower than either the ssnmDBM1 address space or the ssnmMSTR address space.

ssnmSPAS

The Db2 stored procedures address space is responsible for processing stored procedures.

Allied address spaces
Allied agent address spaces ire responsible for handling global lock requests and requests to read from the group buffer pool.