Macros specific to the access methods

The following access methods exist:

• BTAM

• DIV

• EAM

• FASTPAM

• SAM

• ISAM

• UPAM

In the tables below the macros for file access are assigned to the various access methods.

UPAM = User Primary Access Method

The basis for file processing is the standard block (= PAM page). UPAM supports blockoriented file access. One or more logical blocks or parts of logical blocks are transferred. UPAM can also be used to process files that were not created with UPAM.

Macro	Brief description
PAM	Controls all UPAM accesses
For event-driven processing, the following macros are also significant (for a detailed description, see the “Executive Macros” manual [2 (Related publications)]):
CHKEI	Checks the queue status for an event item.
CONTXT	Accesses the register set of the interrupted task/process.
DISCO	Closes the routine for the contingency process.
DISEI	Disconnects the user program from the event item.
ENACO	Opens a routine as a contingency process and assigns it a name and a priority.
ENAEI	Creates an event item and/or establishes the link between the calling process and the event item.
FECB	Creates a file event control block.
LEVCO	Changes the priority of the called process.
POSSIG	Signals an event.
RETCO	Terminates the calling contingency process.
SOLSIG	Requests a signal from the event item.
SUSPEND	Places the calling process in an interruptible wait state.

FASTPAM = Fast Primary Access Method

The basis for file processing is the standard block (= PAM page). The basis for file processing is the standard block (= PAM page). FASTPAM supports block-oriented file access. One or more logical blocks or parts of logical blocks are transferred. FASTPAM can also be used to process files that were not created with FASTPAM.

Macro	Brief description
FPAMSRV	Management functions enable the system environment (FASTPAM environment) enable I/O areas (FASTPAM I/O area pool) open a file for processing close a file opened with FPAMSRV disable the system environment (FASTPAM environment) disable I/O areas (FASTPAM I/O area pool)
FPAMACC	File access functions synchronous reading and writing of logical blocks asynchronous reading and writing of logical blocks wait for the end of asynchronous I/O jobs report the end of asynchronous I/O jobs

DIV = Data In Virtual

DIV allows files to be mapped directly to a virtual address space. Transfer is performed “on demand”, initiated by a page fault when accessing a memory page in a window. DIV can also be used to process files that were not created with DIV.

Macro	Brief description
DIV	Process files with the DIV access method open a file define a window (i.e. a work area in virtual address space) write modified pages from the window back to the file on disk undo changes in the window release windows in virtual address space close a file, releasing any existing windows with default values, if applicable

SAM = Sequential Access Method

A SAM file is a sequence of records (contained in logical blocks). DMS allows the user to process records sequentially in either direction (beginning-of-file to end-of-file or vice versa). For tape processing, SAM complies with all requirements of DIN 66029 up to exchange level 3. Files with either standard or nonstandard blocks can be processed.

Macro	Brief description
FEOV	Initiates a tape swap.
GET	Retrieves the next record.
PUT	Writes the next record to the current end of the file.
PUTX	(Locate mode only) replaces a record in the buffer to which processing has been positioned by means of GET.
RELSE	Terminates a data block.
SETL	Positions to beginning-of-file, to end-of-file, or to a record which is to be retrieved by means of GET.

BTAM = Basic Tape Access Method

BTAM is an access method for block-oriented tape processing; it can also be used to process tape files which were not created with BTAM. During processing of a tape file, the direction in which the file is processed can be changed as desired, and tapes can be positioned to any desired block or section. BTAM processes files with or without standard blocks.

Macro	Brief description
BTAM	Controls all BTAM actions.
FEOV	Initiates a tape swap.
NDWERINF	Interrogates the status bytes.

EAM = Evanescent Access Method

EAM is used to process temporary files in the SYSEAM area. It is a block-oriented access method and is particularly suitable for rapid processing of job-specific work files.

Macro	Brief description
EAM	Controls all EAM accesses

ISAM = Indexed-Sequential Access Method

An ISAM file consists of a set of records. Each record contains a key and the keys are the criterion for sorting the records into blocks. The highest key in each index or data block is placed, together with the block number, in an index block at the next higher level of the index.

Macro	Brief description
ELIM	Deletes a record from the file.
GET	Reads the next record from the file (sequential read).
GETFL	If flagged ISAM keys are used: reads the next record within the flag range (sequentially).
GETKY	Reads the first record with the specified key.
GETR	Reads the previous record (sequential reverse read).
INSRT	Inserts a record into the file with a new ISAM key.
ISREQ	Clears an ISAM lock.
OSTAT	Informs the caller about the number and type of concurrent file accesses.
PUT	Sequentially writes records to the end of the file (and also checks that the keys are in the right order).
PUTX	Replaces a record read by means of GET or a similar macro.
RETRY	After execution of the EXLST PGLOCK exit, resets the ISAM pointer and repeats the last macro.
SETL	Positions the ISAM pointer to the beginning of the file, to the end of the file or to a specific record for subsequent sequential processing.
STORE	Inserts a record into the file with a new ISAM key. Overwrites a record with an existing ISAM key if duplicate ISAM keys are not permitted, or Inserts into the file a record with an existing ISAM key as the last record with this key.

The ISAM pool macros are listed on "Controlling file processing".