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 BINARY(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 Databridge Engine Read Active Audit option, Databridge can access the current audit file. If you do not set Read Active Audit = true in the Databridge Engine 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.
Batch Console
The Batch Console automates routine Client tasks by allowing command files/shell scripts launched by the Databridge Client Manager to interact with the service.
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 Director
Databridge Director (also referred to as DBDirector) is a Windows Service installed with Enterprise Server that starts Enterprise Server whenever a connection request is received.
When you start your computer, DBDirector starts and reads the ListenPort registry value to determine which TCP/IP port communicates with Databridge Clients.
Databridge Engine
Databridge Engine is a generic term that can refer to either DBEngine or the engine component of Databridge Enterprise Server. The two are interchangeable as far as the Databridge Client is concerned.
Databridge Server
Databridge Server is a generic term that can refer to either DBServer or Databridge Enterprise Server. The two are interchangeable as far as the Databridge Client is concerned.
DBClntCfgServer
A program that handles all requests from the Administrative Console specific to a data source. These requests include updating the Client configuration file, and providing access to the Client control tables. Like DBClient, this program is run by the Client Manager service as a background run.
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:
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Databridge Engine and Databridge Enterprise Server
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Databridge Engine 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 Databridge Engine.
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.
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.
primary database
This is the original DMSII database that resides on the host. Databridge replicates from the primary database to one or more Client databases. The Client databases can be another DMSII database or one of several relational databases. Compare this to the replicated (or secondary) database.
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 file format conversion and record format conversion.
replicated database
The replicated database is the database that usually resides on the Client machine and contains records cloned from the DMSII database. The replicated database is updated periodically with changes made to the primary (original) DMSII database. The periodic update (or tracking process) is explained later in this section. Compare this to the primary database.
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.
secondary database
The replicated database. The replicated database is the database that usually resides on the Client machine and contains records cloned from the DMSII database. The replicated database is updated periodically with changes made to the primary (original) DMSII database. The periodic update (or tracking process) is explained later in this section. Compare this to the primary database.
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 Administrative 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 that reflects information about the cloned data, such as the audit location and format level.
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.
visible RSN
An RSN (record serial number) that is declared in the DASDL. These appear as an item in the data set and are therefore visible to the database user.