Basic direct access method - Revision history

InternetArchiveBot: Rescuing 1 sources and tagging 0 as dead.) #IABot (v2.0.9.5

2023-09-27T18:26:38Z

Rescuing 1 sources and tagging 0 as dead.) #IABot (v2.0.9.5

← Previous revision		Revision as of 18:26, 27 September 2023
Line 47:		Line 47:

	==External links==		==External links==
	* {{cite manual\|publisher=IBM\|title=Introduction to IBM Direct-Access Storage Devices and Organization Methods\|id=GC20-1649-9\|date=February 1974\|url=http://www.bitsavers.org/pdf/ibm/dasd/GC20-1649-9_DASDintro_Dec75.pdf}}		* {{cite manual\|publisher=IBM\|title=Introduction to IBM Direct-Access Storage Devices and Organization Methods\|id=GC20-1649-9\|date=February 1974\|url=http://www.bitsavers.org/pdf/ibm/dasd/GC20-1649-9_DASDintro_Dec75.pdf\|access-date=2012-09-24\|archive-date=2011-03-22\|archive-url=https://web.archive.org/web/20110322195353/http://www.bitsavers.org/pdf/ibm/dasd/GC20-1649-9_DASDintro_Dec75.pdf\|url-status=dead}}

	{{Mainframe I/O access methods}}		{{Mainframe I/O access methods}}

Cornmazes at 21:39, 4 September 2023

2023-09-04T21:39:37Z

← Previous revision		Revision as of 21:39, 4 September 2023
Line 1:		Line 1:
			{{Short description\|Computer access method}}
	'''Basic Direct Access Method''', or '''BDAM''' is an [[access method]] for IBM's [[OS/360 and successors]] computer [[operating systems]] on [[IBM System/360\|System/360]] and later [[IBM mainframe\|mainframes]]. BDAM "consists of routines used in retrieving data from, and storing data onto, [[direct access storage device\|direct access devices]]."<ref name=BDAMLogic>{{cite manual\|publisher=IBM\|title=IBM System/360 Operating System Basic Direct Access Method Program Logic Manual\|id=Y28-6617-3\|date=July 1967\|url=http://www.bitsavers.org/pdf/ibm/360/os/bdam/Y28-6617-3_BDAM_PLM_Jul67.pdf}}</ref>{{rp\|p.5}} BDAM is available on [[OS/360]], [[OS/VS2]], [[MVS]], [[z/OS]], and related high-end operating systems.		'''Basic Direct Access Method''', or '''BDAM''' is an [[access method]] for IBM's [[OS/360 and successors]] computer [[operating systems]] on [[IBM System/360\|System/360]] and later [[IBM mainframe\|mainframes]]. BDAM "consists of routines used in retrieving data from, and storing data onto, [[direct access storage device\|direct access devices]]."<ref name=BDAMLogic>{{cite manual\|publisher=IBM\|title=IBM System/360 Operating System Basic Direct Access Method Program Logic Manual\|id=Y28-6617-3\|date=July 1967\|url=http://www.bitsavers.org/pdf/ibm/360/os/bdam/Y28-6617-3_BDAM_PLM_Jul67.pdf}}</ref>{{rp\|p.5}} BDAM is available on [[OS/360]], [[OS/VS2]], [[MVS]], [[z/OS]], and related high-end operating systems.

Citation bot: Add: website. | Use this bot. Report bugs. | Suggested by Whoop whoop pull up | #UCB_webform 177/668

2022-12-08T04:48:25Z

Add: website. | Use this bot. Report bugs. | Suggested by Whoop whoop pull up | #UCB_webform 177/668

← Previous revision		Revision as of 04:48, 8 December 2022
Line 25:		Line 25:
	BDAM accepts disk addresses as either actual device addresses, as relative track addresses, or as relative block numbers.		BDAM accepts disk addresses as either actual device addresses, as relative track addresses, or as relative block numbers.

	'''Device addresses''' are eight byte fields in the form '''MBBCCHHR'''. All subfields are binary numbers.<ref>{{cite web\|last=IBM Corporation \|title=Executing Direct Access Programs \|url=https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.3.0/com.ibm.zos.v2r3.idas300/xdapx.htm}}</ref>		'''Device addresses''' are eight byte fields in the form '''MBBCCHHR'''. All subfields are binary numbers.<ref>{{cite web\|last=IBM Corporation \|title=Executing Direct Access Programs \|website=[[IBM]] \|url=https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.3.0/com.ibm.zos.v2r3.idas300/xdapx.htm}}</ref>
	* '''M''' is the ''extent number'' for files with more than one ''extent'' (non-contiguous files).		* '''M''' is the ''extent number'' for files with more than one ''extent'' (non-contiguous files).
	* '''BB''' is zero. Previously this indicated the ''bin'' on an [[IBM 2321 Data Cell]].		* '''BB''' is zero. Previously this indicated the ''bin'' on an [[IBM 2321 Data Cell]].

Peter Flass: link extent, volume, plus syntax correction

2019-06-25T16:51:59Z

link extent, volume, plus syntax correction

← Previous revision		Revision as of 16:51, 25 June 2019
Line 14:		Line 14:

	==Application program interface==		==Application program interface==
	The programmer specifies <code>DSORG=DA</code> in his [[Data Control Block]] (DCB) to indicate use of BDAM. Space can be in up to 16 extents on each volume. The data set (equivalent to a "file") can reside in up to 255 extents across multiple volumes. If the application has a dependency on the space being on contiguous tracks, you can allocate space for the direct data set in [[Contiguous data storage\|contiguous]] tracks by coding <code>SPACE=(,,CONTIG)</code> on the DD statement.		The programmer specifies <code>DSORG=DA</code> in his [[Data Control Block]] (DCB) to indicate use of BDAM. Space can be in up to 16 [[Extent (file systems)\|extents]] on each [[Volume (computing)\|volume]]. The data set (equivalent to a "file") can reside in up to 255 extents across multiple volumes. If the application has a dependency on the space being on contiguous tracks, you can allocate space for the direct data set in [[Contiguous data storage\|contiguous]] tracks by coding <code>SPACE=(,,CONTIG)</code> on the DD statement.

	Direct data sets must be preformatted before use by opening it as output and writing all the blocks sequentially. This can load all "dummy" records or load initial data.<ref name="ibm">[http://publib.boulder.ibm.com/infocenter/cicsts/v3r1/index.jsp?topic=/com.ibm.cics.ts31.doc/dfha2/dfha24f.htm CICS and BDAM], IBM infocenter</ref>		Direct data sets must be preformatted before use by opening them as output and writing all the blocks sequentially. This can load all "dummy" records or load initial data.<ref name="ibm">[http://publib.boulder.ibm.com/infocenter/cicsts/v3r1/index.jsp?topic=/com.ibm.cics.ts31.doc/dfha2/dfha24f.htm CICS and BDAM], IBM infocenter</ref>

	As a ''basic'' access method BDAM reads and writes member data in [[Block (data storage)\|blocks]] and the I/O operation proceeds [[Asynchronous I/O\|asynchronously]] and must be tested for completion using the <code>CHECK</code> macro.<ref name=Macro>{{cite book\|last1=IBM Corporation\|title=OS Data Management Macro Instructions\|date=June 1973\|url=http://bitsavers.informatik.uni-stuttgart.de/pdf/ibm/360/os/R21.7_Apr73/GC26-3794-1_OS_Data_Management_Macro_Instructions_Rel_21.7_Jun73.pdf\|accessdate=August 19, 2016}}</ref> BDAM uses the standard system macros <code>OPEN</code>, <code>CLOSE</code>, <code>READ</code>, <code>WRITE</code>,and <code>CHECK</code>. The <code>READ</code> or <code>WRITE</code> [[macro instruction]]s must provide the block address or key of the desired record. The <code>CHECK</code> macro has to be used to wait for completion of a specific operation before the data can be accessed or the [[data buffer]] reused. It is possible to start multiple input/output operations to run concurrently.		As a ''basic'' access method BDAM reads and writes member data in [[Block (data storage)\|blocks]] and the I/O operation proceeds [[Asynchronous I/O\|asynchronously]] and must be tested for completion using the <code>CHECK</code> macro.<ref name=Macro>{{cite book\|last1=IBM Corporation\|title=OS Data Management Macro Instructions\|date=June 1973\|url=http://bitsavers.informatik.uni-stuttgart.de/pdf/ibm/360/os/R21.7_Apr73/GC26-3794-1_OS_Data_Management_Macro_Instructions_Rel_21.7_Jun73.pdf\|accessdate=August 19, 2016}}</ref> BDAM uses the standard system macros <code>OPEN</code>, <code>CLOSE</code>, <code>READ</code>, <code>WRITE</code>,and <code>CHECK</code>. The <code>READ</code> or <code>WRITE</code> [[macro instruction]]s must provide the block address or key of the desired record. The <code>CHECK</code> macro has to be used to wait for completion of a specific operation before the data can be accessed or the [[data buffer]] reused. It is possible to start multiple input/output operations to run concurrently.

WRhoten: /* Application program interface */

2019-06-24T20:25:46Z

Application program interface

← Previous revision		Revision as of 20:25, 24 June 2019
Line 14:		Line 14:

	==Application program interface==		==Application program interface==
	The programmer specifies <code>DSORG=DA</code> in his [[Data Control Block]] (DCB) to indicate use of BDAM. Space ~~for~~ a ~~''direct''~~ ~~file~~ (~~accessed~~ by ~~BDAM~~) ~~must~~ be ~~allocated~~ in [[Contiguous data storage\|contiguous]] tracks by coding <code>SPACE=(,,CONTIG)</code> in the DD statement.		The programmer specifies <code>DSORG=DA</code> in his [[Data Control Block]] (DCB) to indicate use of BDAM. Space can be in up to 16 extents on each volume. The data set (equivalent to a "file") can reside in up to 255 extents across multiple volumes. If the application has a dependency on the space being on contiguous tracks, you can allocate space for the direct data set in [[Contiguous data storage\|contiguous]] tracks by coding <code>SPACE=(,,CONTIG)</code> on the DD statement.

	Direct ~~files~~ must be preformatted before use by opening ~~the file~~ as output and writing all the blocks sequentially. This can load all "dummy" records or load initial data.<ref name="ibm">[http://publib.boulder.ibm.com/infocenter/cicsts/v3r1/index.jsp?topic=/com.ibm.cics.ts31.doc/dfha2/dfha24f.htm CICS and BDAM], IBM infocenter</ref>		Direct data sets must be preformatted before use by opening it as output and writing all the blocks sequentially. This can load all "dummy" records or load initial data.<ref name="ibm">[http://publib.boulder.ibm.com/infocenter/cicsts/v3r1/index.jsp?topic=/com.ibm.cics.ts31.doc/dfha2/dfha24f.htm CICS and BDAM], IBM infocenter</ref>

	As a ''basic'' access method BDAM reads and writes member data in [[Block (data storage)\|blocks]] and the I/O operation proceeds [[Asynchronous I/O\|asynchronously]] and must be tested for completion using the <code>CHECK</code> macro.<ref name=Macro>{{cite book\|last1=IBM Corporation\|title=OS Data Management Macro Instructions\|date=June 1973\|url=http://bitsavers.informatik.uni-stuttgart.de/pdf/ibm/360/os/R21.7_Apr73/GC26-3794-1_OS_Data_Management_Macro_Instructions_Rel_21.7_Jun73.pdf\|accessdate=August 19, 2016}}</ref> BDAM uses the standard system macros <code>OPEN</code>, <code>CLOSE</code>, <code>READ</code>, <code>WRITE</code>,and <code>CHECK</code>. The <code>READ</code> or <code>WRITE</code> [[macro instruction]]s must provide the block address of the desired record. The <code>CHECK</code> macro has to be used to wait for completion of a specific operation before the data can be accessed or the [[data buffer]] reused. It is possible to start multiple input/output operations to run concurrently.		As a ''basic'' access method BDAM reads and writes member data in [[Block (data storage)\|blocks]] and the I/O operation proceeds [[Asynchronous I/O\|asynchronously]] and must be tested for completion using the <code>CHECK</code> macro.<ref name=Macro>{{cite book\|last1=IBM Corporation\|title=OS Data Management Macro Instructions\|date=June 1973\|url=http://bitsavers.informatik.uni-stuttgart.de/pdf/ibm/360/os/R21.7_Apr73/GC26-3794-1_OS_Data_Management_Macro_Instructions_Rel_21.7_Jun73.pdf\|accessdate=August 19, 2016}}</ref> BDAM uses the standard system macros <code>OPEN</code>, <code>CLOSE</code>, <code>READ</code>, <code>WRITE</code>,and <code>CHECK</code>. The <code>READ</code> or <code>WRITE</code> [[macro instruction]]s must provide the block address or key of the desired record. The <code>CHECK</code> macro has to be used to wait for completion of a specific operation before the data can be accessed or the [[data buffer]] reused. It is possible to start multiple input/output operations to run concurrently.

	Records in a direct ~~file~~ can contain user-specified ''recorded keys'' of up to 255 bytes—all keys in a file must be the same length. Reads and writes can specify a key in addition to a disk address, and BDAM will search starting at the requested block up to the entire area of the file for a record with a matching key.<ref name=DataMgmt /> This allows multiple keys [[Hash function\|hashing]] to the same track to be handled automatically by the I/O subsystem.		Records in a direct data set can contain user-specified ''recorded keys'' of up to 255 bytes—all keys in a file must be the same length. Reads and writes can specify a key in addition to a disk address, and BDAM will search starting at the requested block up to the entire area of the file for a record with a matching key.<ref name=DataMgmt /> This allows multiple keys [[Hash function\|hashing]] to the same track to be handled automatically by the I/O subsystem.

	==Disk addresses==		==Disk addresses==

Rvdheij: Corrected the URL, z/OS 2.3 will hold for another few years. But this approach with deep links is a dead end.

2019-04-12T12:16:52Z

Corrected the URL, z/OS 2.3 will hold for another few years. But this approach with deep links is a dead end.

← Previous revision		Revision as of 12:16, 12 April 2019
Line 25:		Line 25:
	BDAM accepts disk addresses as either actual device addresses, as relative track addresses, or as relative block numbers.		BDAM accepts disk addresses as either actual device addresses, as relative track addresses, or as relative block numbers.

	'''Device addresses''' are eight byte fields in the form '''MBBCCHHR'''. All subfields are binary numbers.<ref>{{cite web\|last=IBM Corporation \|title=Executing Direct Access Programs \|url=~~http~~://~~publib.boulder~~.ibm.com/~~infocenter~~/~~zos~~/~~v1r11~~/~~index~~.~~jsp?topic=~~/com.ibm.zos.~~r11~~.idas300/xdapx.htm ~~\|accessdate=September 23, 2012 }}{{dead link\|date=October 2016 \|bot=InternetArchiveBot \|fix-attempted=yes~~ }}</ref>		'''Device addresses''' are eight byte fields in the form '''MBBCCHHR'''. All subfields are binary numbers.<ref>{{cite web\|last=IBM Corporation \|title=Executing Direct Access Programs \|url=https://www.ibm.com/support/knowledgecenter/en/SSLTBW_2.3.0/com.ibm.zos.v2r3.idas300/xdapx.htm}}</ref>
	* '''M''' is the ''extent number'' for files with more than one ''extent'' (non-contiguous files).		* '''M''' is the ''extent number'' for files with more than one ''extent'' (non-contiguous files).
	* '''BB''' is zero. Previously this indicated the ''bin'' on an [[IBM 2321 Data Cell]].		* '''BB''' is zero. Previously this indicated the ''bin'' on an [[IBM 2321 Data Cell]].

Certes: Disambiguating links to Contiguity (link changed to Contiguous data storage) using DisamAssist.

2018-05-14T19:11:58Z

Disambiguating links to Contiguity (link changed to Contiguous data storage) using DisamAssist.

← Previous revision		Revision as of 19:11, 14 May 2018
Line 14:		Line 14:

	==Application program interface==		==Application program interface==
	The programmer specifies <code>DSORG=DA</code> in his [[Data Control Block]] (DCB) to indicate use of BDAM. Space for a ''direct'' file (accessed by BDAM) must be allocated in [[~~Contiguity#Computer~~ ~~science~~\|contiguous]] tracks by coding <code>SPACE=(,,CONTIG)</code> in the DD statement.		The programmer specifies <code>DSORG=DA</code> in his [[Data Control Block]] (DCB) to indicate use of BDAM. Space for a ''direct'' file (accessed by BDAM) must be allocated in [[Contiguous data storage\|contiguous]] tracks by coding <code>SPACE=(,,CONTIG)</code> in the DD statement.

	Direct files must be preformatted before use by opening the file as output and writing all the blocks sequentially. This can load all "dummy" records or load initial data.<ref name="ibm">[http://publib.boulder.ibm.com/infocenter/cicsts/v3r1/index.jsp?topic=/com.ibm.cics.ts31.doc/dfha2/dfha24f.htm CICS and BDAM], IBM infocenter</ref>		Direct files must be preformatted before use by opening the file as output and writing all the blocks sequentially. This can load all "dummy" records or load initial data.<ref name="ibm">[http://publib.boulder.ibm.com/infocenter/cicsts/v3r1/index.jsp?topic=/com.ibm.cics.ts31.doc/dfha2/dfha24f.htm CICS and BDAM], IBM infocenter</ref>

70.62.97.98 at 20:31, 23 January 2018

2018-01-23T20:31:55Z

← Previous revision		Revision as of 20:31, 23 January 2018
Line 5:		Line 5:

	With BDAM, "the programmer can directly store and retrieve a block by specifying either		With BDAM, "the programmer can directly store and retrieve a block by specifying either
	its actual [[#Disk_addresses\|device address]], its [[#Disk_addresses\|relative position]] within a data set (relative block number), or the [[#Disk_addresses\|relative track]] within a data set at which the system is to begin a		its actual [[#Disk_addresses\|device address]], its [[#Disk_addresses\|relative position]] within a data set (relative block number), or the [[#Disk_addresses\|relative track]] within a data set at which the system is to begin a search.<ref name=DataMgmt />{{rp\|p.63}}
	search.<ref name=DataMgmt />{{rp\|p.63}}

	BDAM provides no index or structure to the file except as programmed by the application. In many applications, a hashing or randomizing function may be used to assign the block address based on a key in the data. If physical [[Count Key Data\|keys]] are used, the key of the last record within the block must be written as the key for that block.		BDAM provides no index or structure to the file except as programmed by the application. In many applications, a hashing or randomizing function may be used to assign the block address based on a key in the data. If physical [[Count Key Data\|keys]] are used, the key of the last record within the block must be written as the key for that block.

John of Reading: Typo fixing, replaced: all all → all the using AWB

2016-12-18T15:52:09Z

Typo fixing, replaced: all all → all the using AWB

← Previous revision		Revision as of 15:52, 18 December 2016
Line 17:		Line 17:
	The programmer specifies <code>DSORG=DA</code> in his [[Data Control Block]] (DCB) to indicate use of BDAM. Space for a ''direct'' file (accessed by BDAM) must be allocated in [[Contiguity#Computer science\|contiguous]] tracks by coding <code>SPACE=(,,CONTIG)</code> in the DD statement.		The programmer specifies <code>DSORG=DA</code> in his [[Data Control Block]] (DCB) to indicate use of BDAM. Space for a ''direct'' file (accessed by BDAM) must be allocated in [[Contiguity#Computer science\|contiguous]] tracks by coding <code>SPACE=(,,CONTIG)</code> in the DD statement.

	Direct files must be preformatted before use by opening the file as output and writing all ~~all~~ blocks sequentially. This can load all "dummy" records or load initial data.<ref name="ibm">[http://publib.boulder.ibm.com/infocenter/cicsts/v3r1/index.jsp?topic=/com.ibm.cics.ts31.doc/dfha2/dfha24f.htm CICS and BDAM], IBM infocenter</ref>		Direct files must be preformatted before use by opening the file as output and writing all the blocks sequentially. This can load all "dummy" records or load initial data.<ref name="ibm">[http://publib.boulder.ibm.com/infocenter/cicsts/v3r1/index.jsp?topic=/com.ibm.cics.ts31.doc/dfha2/dfha24f.htm CICS and BDAM], IBM infocenter</ref>

	As a ''basic'' access method BDAM reads and writes member data in [[Block (data storage)\|blocks]] and the I/O operation proceeds [[Asynchronous I/O\|asynchronously]] and must be tested for completion using the <code>CHECK</code> macro.<ref name=Macro>{{cite book\|last1=IBM Corporation\|title=OS Data Management Macro Instructions\|date=June 1973\|url=http://bitsavers.informatik.uni-stuttgart.de/pdf/ibm/360/os/R21.7_Apr73/GC26-3794-1_OS_Data_Management_Macro_Instructions_Rel_21.7_Jun73.pdf\|accessdate=August 19, 2016}}</ref> BDAM uses the standard system macros <code>OPEN</code>, <code>CLOSE</code>, <code>READ</code>, <code>WRITE</code>,and <code>CHECK</code>. The <code>READ</code> or <code>WRITE</code> [[macro instruction]]s must provide the block address of the desired record. The <code>CHECK</code> macro has to be used to wait for completion of a specific operation before the data can be accessed or the [[data buffer]] reused. It is possible to start multiple input/output operations to run concurrently.		As a ''basic'' access method BDAM reads and writes member data in [[Block (data storage)\|blocks]] and the I/O operation proceeds [[Asynchronous I/O\|asynchronously]] and must be tested for completion using the <code>CHECK</code> macro.<ref name=Macro>{{cite book\|last1=IBM Corporation\|title=OS Data Management Macro Instructions\|date=June 1973\|url=http://bitsavers.informatik.uni-stuttgart.de/pdf/ibm/360/os/R21.7_Apr73/GC26-3794-1_OS_Data_Management_Macro_Instructions_Rel_21.7_Jun73.pdf\|accessdate=August 19, 2016}}</ref> BDAM uses the standard system macros <code>OPEN</code>, <code>CLOSE</code>, <code>READ</code>, <code>WRITE</code>,and <code>CHECK</code>. The <code>READ</code> or <code>WRITE</code> [[macro instruction]]s must provide the block address of the desired record. The <code>CHECK</code> macro has to be used to wait for completion of a specific operation before the data can be accessed or the [[data buffer]] reused. It is possible to start multiple input/output operations to run concurrently.

Gah4: /* Application program interface */ Remove duplicate statement.

2016-10-28T03:22:15Z

Application program interface: Remove duplicate statement.

← Previous revision		Revision as of 03:22, 28 October 2016
Line 19:		Line 19:
	Direct files must be preformatted before use by opening the file as output and writing all all blocks sequentially. This can load all "dummy" records or load initial data.<ref name="ibm">[http://publib.boulder.ibm.com/infocenter/cicsts/v3r1/index.jsp?topic=/com.ibm.cics.ts31.doc/dfha2/dfha24f.htm CICS and BDAM], IBM infocenter</ref>		Direct files must be preformatted before use by opening the file as output and writing all all blocks sequentially. This can load all "dummy" records or load initial data.<ref name="ibm">[http://publib.boulder.ibm.com/infocenter/cicsts/v3r1/index.jsp?topic=/com.ibm.cics.ts31.doc/dfha2/dfha24f.htm CICS and BDAM], IBM infocenter</ref>

	As a ''basic'' access method BDAM reads and writes member data in [[Block (data storage)\|blocks]] and the I/O operation proceeds [[Asynchronous I/O\|asynchronously]] and must be tested for completion using the <code>CHECK</code> macro.<ref name=Macro>{{cite book\|last1=IBM Corporation\|title=OS Data Management Macro Instructions\|date=June 1973\|url=http://bitsavers.informatik.uni-stuttgart.de/pdf/ibm/360/os/R21.7_Apr73/GC26-3794-1_OS_Data_Management_Macro_Instructions_Rel_21.7_Jun73.pdf\|accessdate=August 19, 2016}}</ref> BDAM uses the standard system macros <code>OPEN</code>, <code>CLOSE</code>, <code>READ</code>, <code>WRITE</code>,and <code>CHECK</code>. The <code>READ</code> or <code>WRITE</code> [[macro instruction]]s must provide the block address of the desired record. The <code>CHECK</code> macro has to be used to wait for completion of a specific operation before the data can be accessed or the [[data buffer]] reused. It is possible to start multiple input/output operations to run concurrently~~; the <code>CHECK</code> macro has to be used to wait for completion of a specific operation before the data can be accessed or the [[data buffer]] reused~~.		As a ''basic'' access method BDAM reads and writes member data in [[Block (data storage)\|blocks]] and the I/O operation proceeds [[Asynchronous I/O\|asynchronously]] and must be tested for completion using the <code>CHECK</code> macro.<ref name=Macro>{{cite book\|last1=IBM Corporation\|title=OS Data Management Macro Instructions\|date=June 1973\|url=http://bitsavers.informatik.uni-stuttgart.de/pdf/ibm/360/os/R21.7_Apr73/GC26-3794-1_OS_Data_Management_Macro_Instructions_Rel_21.7_Jun73.pdf\|accessdate=August 19, 2016}}</ref> BDAM uses the standard system macros <code>OPEN</code>, <code>CLOSE</code>, <code>READ</code>, <code>WRITE</code>,and <code>CHECK</code>. The <code>READ</code> or <code>WRITE</code> [[macro instruction]]s must provide the block address of the desired record. The <code>CHECK</code> macro has to be used to wait for completion of a specific operation before the data can be accessed or the [[data buffer]] reused. It is possible to start multiple input/output operations to run concurrently.

	Records in a direct file can contain user-specified ''recorded keys'' of up to 255 bytes—all keys in a file must be the same length. Reads and writes can specify a key in addition to a disk address, and BDAM will search starting at the requested block up to the entire area of the file for a record with a matching key.<ref name=DataMgmt /> This allows multiple keys [[Hash function\|hashing]] to the same track to be handled automatically by the I/O subsystem.		Records in a direct file can contain user-specified ''recorded keys'' of up to 255 bytes—all keys in a file must be the same length. Reads and writes can specify a key in addition to a disk address, and BDAM will search starting at the requested block up to the entire area of the file for a record with a matching key.<ref name=DataMgmt /> This allows multiple keys [[Hash function\|hashing]] to the same track to be handled automatically by the I/O subsystem.