Functions of DML Statements

Data Manipulation Language Statements › Functions of DML Statements

Functions of DML Statements

The data manipulation language enables you to access the database management system (DBMS) and to request LRF and DC/UCF services from your Assembler program. The DML statements can be grouped into 14 categories by function:

Control statements perform the following:
- Initiate and terminate processing
- Effect recovery
- Prevent concurrent retrieval and update of database records
- Evaluate set conditions
Retrieval statements locate records in the database and make them available to the application program.
Modification statements add new records to the database and modify and delete existing records.
Accept statements allow you to move special information such as database keys, storage addresses, and statistics from the DBMS to the application program's variable storage.
Logical-record statements allow you to retrieve, modify, store, and erase logical records created through Logical Record Facility.
Program management statements perform the following:
- Pass and return control from one program to another
- Load and delete programs and tables
- Define exit routines to be performed before an abnormal program termination (abend)
- Force an abend condition
Storage management statements allocate and release variable storage.
Task management statements perform the following:
- Initiate a new task
- Change the dispatching priority of the issuing task
- Enqueue and dequeue system resources
- Signal that a task is to wait pending completion of an event
- Post an event control block (ECB) indicating completion of an event
Time management statements obtain the time and date and set up time-related events. These events include:
- Placing the issuing task in a wait state for a specified time
- Posting a user-specified ECB after a specified interval
- Initiating a new task after a specified interval
Scratch management statements create, delete, or retrieve records from the scratch area.
Queue management statements create, delete, or retrieve records from the queue area.
Terminal management statements transfer data between the application program and a terminal or printer.
Utility function statements perform the following:
- Request retrieval of task-related information
- Request a memory dump of selected parts of storage
- Retrieve and send a predefined message stored in the dictionary
- Send a specified message to one or more users or logical terminals
- Collect, retrieve, and write DC/UCF system statistics on a transaction basis
- Establish long-term database locks and monitor access to database records used across tasks in a pseudo-conversational transaction
Recovery statements perform functions relating to database, scratch, and queue area recovery in the event of a system failure. These functions perform the following:
- Establish checkpoints on the journal file for database, scratch, and queue records used by the issuing task
- Roll back user database, scratch, and queue record areas to the last checkpoint established
- Establish an end-of-task checkpoint and relinquish control of all database, scratch, and queue record areas associated with the issuing task
- Write user defined records to the journal file

The following table groups the DML statements by function and gives a brief description of each command.

DML Statements Grouped by Function

Function	DML statement	Description
Control Statements	@BIND SUBSCH	Signs on the application program to the CA IDMS/DB database management system
	@BIND REC	Establishes addressability in variable storage for one or more records included in the program's subschema
	@BIND PROC	Establishes communication between the application program and a DBA-defined database procedure
	@READY	Prepares database areas for processing
	@FINISH	Commits changes made to the database through an individual run unit and terminates the run unit
	@IF	Evaluates the presence of records in a set and specifies action based on the outcome
	@COMMIT	Commits changes made to the database by an individual run unit
	@ROLLBAK	Rolls back uncommitted changes made to the database through an individual run unit
	@KEEP	Places locks on record occurrences
Retrieval Statements	@FIND/OBTAIN DBKEY	Accesses a record by using a db-key previously saved by the program
	@FIND/OBTAIN CURRENT	Accesses a record by using established currencies
	@FIND/OBTAIN WITHIN SET/AREA	Accesses a record based on its logical location within a set or its physical location within an area
	@FIND/OBTAIN OWNER	Accesses the owner record of a set occurrence
	@FIND/OBTAIN CALC/DUPLICATE	Accesses a record by using its CALC-key value
	@FIND/OBTAIN USING SORT KEY	Accesses a record in a sorted set by using its sort-key value
	@GET	Moves all data associated with a previously located record into program variable storage
Modification Statements	@STORE	Adds a new record to the database
	@MODIFY	Changes the contents of an existing record
	@CONNECT	Links a record to a set
	@DISCON	Removes a member record from a set
	@ERASE	Deletes a record from the database
Accept Statements	@ACCEPT DBKEY FROM CURRENCY	Saves the db-key of the current record of run unit, record type, set, or area
	@ACCEPT DBKEY RELATIVE TO CURRENCY	Saves the db-key of the next, prior, or owner record relative to the current record of a set
	@ACCEPT PAGE INFORMATION FOR A GIVEN RECORD	Saves the page information for a record current record of a set
	@ACCEPT STATS	Returns system runtime statistics to the program
	@ACCEPT BIND	Returns a record's bind address to the program
	@ACCEPT PGINFO	Returns page information for a given record to the program
	@ACCEPT PROC	Returns information in the application program information block associated with a database procedure to the program
	@RETURN	Retrieves a database key of a record entry that has been indexed under integrated indexing.
Logical Record Facility (LRF) Statements	@OBTAIN logical-record @MODIFY logical-record @STORE logical-record @ERASE logical-record	Retrieves a logical record Modifies a logical record Stores a new logical record Deletes a logical record
Program Management Statements	#LINK	Passes control to another program with the expectation of receiving it back
	#RETURN	Returns control to the next higher level calling program
	#LOAD	Loads a program or table into the program pool
	#DELETE	Signals that the program has finished using a program or table in the program pool
	#STAE	Establishes linkage to a program or routine that will receive control in the event of an abend
	#ABEND	Abnormally terminates the issuing task
	#XCTL	Passes control to another program with no expectation of having it returned
Storage Management Statements	#GETSTG #FREESTG	Allocates variable storage from a DC/UCF storage pool Frees all or part of a block of variable storage
Task Management Statements	#ATTACH	Attaches a new task within the DC/UCF system
	#CHAP	Changes the dispatching priority of the issuing task
	#ENQ	Acquires a resource or a list of resources
	#DEQ	Releases a resource
	#WAIT	Relinquishes control to the system while awaiting the completion of an event
	#POST	Posts an event control block
Time Management Statements	#GETIME	Obtains the time and date from the system
	#SETIME	Defines a timed event
Scratch Management Statements	#PUTSCR #GETSCR #DELSCR	Stores a scratch record Retrieves a scratch record Deletes a scratch record
Queue Management Statements	#PUTQUE #GETQUE #DELQUE	Stores a queue record Retrieves a queue record Deletes a queue record
Terminal Management (Basic Mode)	#TREQ	Transfers data and device dependent information to or from the terminal, or establishes a terminal request block (TRB) for use by subsequent #TREQ operations. The #TREQ statement can be used to communicate in an SNA network environment
Terminal Management (Line Mode)	#LINEIN	Requests a synchronous data transfer from the terminal to the issuing program
	#LINEOUT	Requests a synchronous or asynchronous data transfer from the issuing program to the terminal
	#LINEEND	Terminates the current line I/O session
Terminal Management (Mapping Mode)	#MREQ	Requests a transfer of data from the issuing program to the terminal and/or vice versa
	#MAPINQ	Obtains information or tests conditions concerning the previous map operation
	#MAPMOD	Requests modifications of mapping options for a map
	#STRTPAG	Begins a map paging session and specifies options for that session
	#ENDPAG	Terminates a map paging session
Terminal Management (Print Mode)	#PRINT	Transfers data from a task to a terminal defined as a printer.
Utility Functions	#ACCEPT	Retrieves task-related information
	#SNAP	Requests a memory dump of selected parts of storage
	#SENDMSG	Sends a message to a user, logical terminal, list of users, or list of logical terminals
	#TRNSTAT	Requests or terminates statistics collection; retrieves transaction statistics into program storage
	#KEEP	Enables database locks or database monitoring for records, sets, or areas or terminates a prior #KEEP request
	#WTL	Retrieves a message from the dictionary and sends it to a predefined destination
Recovery Statements	#COMMIT	Commits changes made to the database through an individual run unit or through all database sessions associated with a task
	#FINISH	Commits changes made to the database through an individual run unit or through all database sessions associated with a task
	#ROLLBAK	Rolls back uncommitted changes made to the database through an individual run unit or through all database sessions associated with a task
	#PUTJRNL	Writes user-defined records to the journal file