DMCLs

Defining Physical Databases › Overview › DMCLs

DMCLs

DMCL Contains Segments

A DMCL contains one or more segments. These may include:

Segments that define the system dictionary
Segments that define one or more application dictionaries
Segments that define one or more user databases

DMCL Used at Runtime

A DMCL is the structure used by CA IDMS/DB at runtime to access physical database definitions. It must exist as a load module in a load library.

Buffers Reserve Space in Memory

A DMCL also defines two types of buffers:

Database buffers, which hold database pages in use by CA IDMS/DB
A journal buffer which holds journal blocks used to log database activity prior to being written to the journal file

Journal Files

Depending on your runtime environment, your DMCL will contain one of the following designations for journaling:

Environment	Journaling entities
Central version Local mode (without journaling)	2 or more disk journals 1 archive journal
Local mode (with journaling)	1 tape journal

Environment

Journaling entities

Central version

Local mode (without journaling)

2 or more disk journals
1 archive journal

Local mode (with journaling)

1 tape journal

Data Sharing Attributes

A DMCL used by a central version that is a member of a data sharing group also specifies attributes that are related to data sharing. These attributes include such things as the maximum number of members that can belong to the group and the action that should be taken if the coupling facility fails. These attributes are ignored by central versions that are not members of a data sharing group and by CA IDMS running in a local mode environment.