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Glossary of Terms

absolute address (AA) value

AA is a DMSII term that stands for absolute address. An absolute address value is an A Series WORD (48-bits in length). In the Databridge Client, AA is the hexadecimal representation (12 character strings containing the characters 0--9 and A--F) of the AA value on the host. Databridge Client uses the AA values to implement unique keys for the parent structures of embedded data set records. It also uses AA values to reference the records of data sets that do not have DMSII SETS with the NO DUPLICATES ALLOWED attribute.

AA values are not constant. Any DMSII reorganization (record conversion, file format, or garbage collection) changes these values.

Databridge Client supports numeric AA values that are stored as NUMBER(15) in Oracle and BIGINT in SQL Server. It also supports binary AA values that are stored as RAW(6) in Oracle and BIN/ARY(6) in SQL Server.

Audit Files

An audit file is created by DMSII and contains the raw format of changes made to the DMSII database by update programs. Audit file records contain the deletes, adds, and modifies that were made to the various structures. It can contain, for example, hours\', days\', or weeks\' worth of information.

Databridge uses the audit file for the raw data of each database change to exactly replicate the primary database. Databridge records the audit location (AFN, ABSN, SEG, IDX) between runs, so it can restart without losing any records.

If you set the DBEngine Read Active Audit option, Databridge can access the current audit file. If you do not set Read Active Audit = true in the DBEngine parameter file, Databridge can access audit information up to and including the current audit file minus one. The audit file contains the update level at the time the audit file was created. The update level in the audit file and the update level in the DESCRIPTION file used by Databridge must match before Databridge will update a replicated database.

When an audit file is closed, DMSII creates the next one in the series. Audit files are closed for several reasons, including the following:

• An operator closes the audit file with the mixnumber SM AUDIT CLOSE command.

• The audit file reaches the file size set in its DASDL.

• There is an I/O error on the audit file.

• There is not enough disk space for this audit file.

• The database update level changes due to database definition changes

• A Databridge accessory closed the file in preparation for the fixup phase after extracting records from a DMSII database.

• The current audit file could not be found.

• A file reorganization was executed to modify the DMSII structure.

audit trail

The audit trail contains all of the audit files generated for a database. The Databridge Engine reads the audit files to extract updates. It then passes the updates to the Client to be applied to the relational database. After the updates have been successfully extracted, the Client saves the state information, which includes the location in the audit trail from which the last group of updates for the data set were read.

caching

A process that filters files before they\'re requested by the Databridge Client. Caching allows Databridge Enterprise Server to send Client data requests quickly and without placing an additional resource burden on the mainframe.

client

The client is the computer system that will receive DMSII records from the primary database. The client could be a Windows computer, a UNIX computer, or an MCP server. The client can have a relational or a DMSII database.

cloning

Cloning is the one-time process of generating a complete snapshot of a data set to another file. Cloning creates a static picture of a dynamic database. Databridge uses the DMSII data sets and the audit trail to ensure that the cloned data represents a synchronized snapshot of the data sets at a quiet point, even though other programs may be updating the database concurrently. Databridge clones only those data sets you specify.

Cloning is one phase of the database replication process. The other phase is tracking (or updating), which is the integration of database changes since the cloning.

DASDL

Data and Structure Definition Language (DASDL) is the language that defines DMSII databases. The DASDL must be compiled to create a DESCRIPTION file.

data set

A data set is a file structure in DMSII in which records are stored. It is similar to a table in a relational database. You can select the data sets you want to store in your replicated database.

Databridge Server

Databridge Server is a generic term that can refer to either DBServer or DBEnterprise Server. The two are interchangeable as far as the Databridge Client is concerned.

DBServer

DBServer is a Databridge Host accessory that responds to Databridge Client requests for DMSII data or DMSII layout information and provides communications between the following components:

  • DBEngine and Databridge Enterprise Server

  • DBEngine and the Databridge Client

    ::: {.note} When Enterprise Server is used with the Databridge Client, Enterprise Server takes over much of the functionality of DBServer and DBEngine. :::

direct disk

A replication method that allows Databridge Enterprise Server to clone and track DMSII data sets without using any significant mainframe resources. Direct disk replication requires a SAN (Storage Area Network) or Logical Disks configured to make MCP disks visible in Windows.

entry point

A procedure in a library object.

extraction

Extraction is the process of reading through a data set sequentially and writing those records to a file (either a secondary database or flat file).

file format conversion

A type of DMSII reorganization affects file size values (for example, AREASIZE, BLOCKSIZE, or TABLESIZE), but it does not change the layout of the records in a DMSII database.

flat files

A flat file is a plain text or mixed text and binary file which usually contains one record per line. Within the record, individual fields may be separated by delimiters, such as commas, or have a fixed length and be separated by padding. An example of a flat file is an address list that contains fields for Name and Address.

garbage collection reorganization

A garbage collection reorganization moves records around, but it doesn't change the layout of the DMSII database. Its primary function is to improve disk and/or I/O efficiency by eliminating the space occupied by deleted records. Optionally, a garbage collection reorganization reorders the remaining records in the same sequence as one of the sets.

Kafka Specific Terms

The following terms are used to describe certain terms that are specifically related to Databridge Client for Kafka.

  • Brokers. Brokers may consist of a small or large cluster of servers running Kafka.

  • Bootstrap Brokers. Brokers that enable a cluster of servers to be accessible through the initial connection.

  • Producers. Producers push and/or publish data to Kafka topics which are managed within a cluster of servers managing topics (Brokers).

  • Topics. Topics are where data (messages) is stored and published to Broker(s). Topics can be published to multiple brokers, and the data can be distributed in different ways through the use of partitions.

lag time

The lag time is defined as the elapsed time between the time a record in the DMSII database is updated and the time where this update appears in the relational database. This value accounts for any difference between the clock on the mainframe and that on the client machine.

mutex

A mutex is an operating system resource that is used to implement a critical section and prevent multiple processes from updating the same variables at the same time.

null record

A record for a data set where every data item is null.

null value

The value defined in the DASDL to be NULL for a data item. If the DASDL does not explicitly specify a NULL value for a data item, the NULL value is all bits turned on.

quiet point (QPT)

A quiet point is a point in the audit trail when the DMSII database is quiet and no program is in transaction state. This can occur naturally, or it can be forced by a DMSII sync point.

record format conversion

A type of DMSII reorganization that occurs when a data set or set (group of keys) is reordered or reformatted. It indicates that changes were made to a data set format, or to data items, such as changing the length of an item, for example, BANK-ID NUMBER (10) to BANK-ID NUMBER (15).

record serial number (RSN)

Record sequence numbers (RSN) are 48-bit quantities used by the Databridge Engine, in the case of DMSII XE, to uniquely identify a record. RSNs will always be used instead of AA values when available except for data sets having embedded data sets. RSNs are always static; they will not change after a garbage collection reorganization.

reorganization

Structural or formatting changes to records in the DMSII database, which may require parallel changes to (or re-cloning of) records in the secondary, or relational, database. See also glossentry_title and glossentry_title.

replication

Replication is the ongoing process of cloning and tracking changes to a DMSII database.

rollback

A systematic restoration of the primary or secondary database to a previous state in which the problem or bad data is no longer found.

semaphores

Operating system resources that are mainly used to implement thread synchronization and signaling.

service

The service (Windows) or daemon (UNIX) that automates most Client operations. It handles operator requests from the Client Console and routes all log and informational messages to the consoles.

set

An index into a data set. A set has an entry (key + pointer) for every record in the data set.

state information

Data stored in the DATASETS Client control table that reflects information about each of the cloned data sets. This information includes the current replication phase (MODE) of the data set. When the data set is successfully extracted, the information also includes the location in the DMSII audit trail from which the last group of updates for the data set was read. This consists of the audit file number (AFN), the audit block sequence number (ABSN), the segment number (SEG) and the index (INX) of the block within the audit file and the timestamp of the block in the audit trail.

structure

A data set, set, subset, access, or remap. Each structure has a unique number called the structure number.

table

A data structure in the client database corresponding to a data set or remap in the host DMSII database.

tracking

Tracking is an ongoing process for propagating changes made to records in the DMSII primary database to the replicated database after the initial clone. The Databridge Engine performs extraction as well as tracking.