DMCL Statement

DMCL statements perform the following tasks:
idms19
DMCL statements perform the following tasks:
  • Create, alters, or deletes the definition of a DMCL in the dictionary
  • Generate a DMCL load module and stores it in the DDLCATLOD area of the dictionary
  • Delete a DMCL load module from the DDLCATLOD area of the dictionary
  • Display or punches the definition of a DMCL in the dictionary
This topic contains the following information on DMCL statements:
2
Authorization
  • To create, alter, drop or generate a DMCL, you must have the following privileges:
    • DBADMIN on the dictionary in which the DMCL definition resides
    • CREATE (for creating), ALTER (for altering and generating), or DROP (for dropping) privilege on the named DMCL
    • To alter a DMCL you must have USE authorization on any dbtable including the DMCL
  • To display or punch a DMCL definition, you must have DISPLAY privilege on the named DMCL or DBADMIN authority on the dictionary in which the DMCL definition resides
  • To associate a database name table with a DMCL, you must have USE privilege for the named database name table
Syntax
CREATE/DROP DMCL
►►──┬─ CREATE ─┬─ DMCL dmcl-name ─────────────────────────────────────────────►◄ └─ DROP ───┘
ALTER DMCL
►►── ALTER DMCL dmcl-name ────────────────────────────────────────────────────► ►──┬────────────────────────────────────────────┬────────────────────────────► └─ DEFAULT BUFFER ─┬─ default-buffer-name ─┬─┘ └─ NULL ◄───────────────┘ ►──┬──────────────────────────────┬──────────────────────────────────────────► └─ DBTABLE ─┬─ dbtable-name ─┬─┘ └─ NULL ◄────────┘ ►──┬────────────────────────────────────────┬────────────────────────────────► │ ┌────────────────────────────────────┐ │ └─▼-─┬─ segment-specification ───────┬─┴─┘ ├─ file-override-specification ─┤ └─ area-override-specification ─┘ ►──┬────────────────────────────────────────────────┬────────────────────────► └─ DATA SHARING ─┬─ NO ──────────────────────────┤ │ ┌───────────────────────────┐ │ └─▼─ data-sharing-attributes ─┴─┘ ►───┬────────────────────────────────────────────────────────────────────────► └─ MEMORY CACHE ─┬──────────────────────────────┬────────────────────────► └─ LOCATION ─┬─ ANYWHERE ◄───┬─┘ └─ 64 BIT ONLY ─┘ ►────────────────────────────────────────────────────────┬───────────────────►◄ ►────────────────────┬──────────────────────────────────┬┘ └─ STORAGE LIMIT ─┬─ OPSYS ◄──────┬┘ └─ nnn ─┬─ MB ─┬┘ ├─ GB ─┤ ├─ TB ─┤ ├─ PB ─┤ └─ EB ─┘
GENERATE DMCL
►►── GENERATE DMCL dmcl-name ─────────────────────────────────────────────────► ►─┬────────────────────┬─────────────────────────────────────────────────────►◄ └─ FOR ─┬─ MVS ◄───┬─┘ ├─ VSE ────┤ └─ VM ─────┘
DELETE DMCL LOAD MODULE
►►─┬─ DELete ─┬─ DMCL LOAD MODULE dmcl-load-module-name ─────────────────────► └─ DROP ───┘ ►─┬─────────────┬───────────────────────────────────────────────────────────►◄ └─ PERMANENT ─┘
DISPLAY/PUNCH DMCL
►►─┬─ DISplay ─┬─ DMCL dmcl-name ─────────────────────────────────────────────► └─ PUNch ───┘ ┌───────────────────────────────────────┐ ►─▼─┬───────────────────────────────────┬─┴──────────────────────────────────► │ ┌────────────────┐ │ ├─ WITh ──────┬─▼─┬─ AREas ────┬─┴──┘ └─ WITHOut ───┘ ├─ BUFfers ──┤ ├─ FILes ────┤ ├─ JOUrnals ─┤ ├─ SEGments ─┤ ├─ DETails ──┤ ├─ HIStory ──┤ ├─ ALL ◄─────┤ └─ NONe ─────┘ ►─┬──────────────────────────┬───────────────────────────────────────────────► └─ VERb ─┬─ DISplay ───┬───┘ ├─ PUNch ─────┤ ├─ CREate ◄───┤ ├─ ALTer ─────┤ └─ DROp ──────┘ ►─┬───────────────────────┬──────────────────────────────────────────────────►◄ └─ AS ─┬─ COMments ◄──┬─┘ └─ SYNtax ─────┘
Expansion of
data-sharing-attributes
►►─┬─ LOCK ENTRIES lock-entry-count ───────────┬──────────────────────────────►◄ ├─ MEMBERS member-count ────────────────────┤ ├─ DEFAULT SHARED CACHE default-cache-name ─┤ └─ CONNECTIVITY LOSS ─┬─ ABEND ─────┬───────┘ └─ NOABEND ◄──┘
Expansion of
segment-specification
►►─┬───────────────┬─ SEGMENT segment-name ───────────────────────────────────► ├─┬─ ADD ◄────┬─┤ │ └─ INClude ─┘ │ └─┬─ DROP ────┬─┘ └─ EXClude ─┘ ►─┬─────────────────────────────────────────────┬────────────────────────────► └─ DEFAULT BUFFER ─┬─ database-buffer-name ─┬─┘ └─ NULL ─────────────────┘ ►─┬──────────────────────────────────────────────────────┬───────────────────► └─ ON STARTUP SET STATUS TO ─┬─ UPDATE ◄─────────────┬─┘ ├─ RETRIEVAL ───────────┤ ├─ TRANSIENT RETRIEVAL ─┤ └─ OFFLINE ─────────────┘ ►─┬──────────────────────────────────────────────────────────────┬───────────► └─ ON WARMSTART ─┬─ MAINTAIN CURRENT STATUS ◄────────────────┬─┘ └─ SET STATUS TO ─┬─ UPDATE ──────────────┬─┘ ├─ RETRIEVAL ───────────┤ ├─ TRANSIENT RETRIEVAL ─┤ └─ OFFLINE ─────────────┘ ►─┬─────────────────────────────────────────────────┬────────────────────────► └─ DEFAULT SHARED CACHE ─┬─ default-cache-name ─┬─┘ └─ NULL ◄──────────────┘ ►─┬───────────────────────────┬──────────────────────────────────────────────►◄ └─ DATA SHARING ─┬─ NO ◄──┬─┘ └─ YES ──┘
Expansion of
file-override-specification
►►─┬───────────────┬─ FILE segment-name.file-name ────────────────────────────► ├─┬─ ADD ◄────┬─┤ │ └─ INClude ─┘ │ └─┬─ DROP ────┬─┘ └─ EXClude ─┘ ►─┬──────────────────────────────────────┬───────────────────────────────────► └─ BUFFER ───┬ database-buffer-name ──┬┘ └─ DEFAULT ◄─────────────┘ ►─┬─────────────────────────────┬────────────────────────────────────────────► └─ ASSIGN TO ─┬─ ddname ────┬─┘ ├─ filename ──┤ ├─ DEFAULT ◄──┤ └─ NULL ──────┘ ►─┬───────────────────────────────┬──────────────────────────────────────────► └─── DISP ─┬─ SHR ───────┬──────┘ └─ OLD ───────┘ ►─┬──────────────────────────────────────────────────────────────────┬───────► └─ MEMORY CACHE ┬──NO ◄─────────────────────────────────────────┬──┘ └─ YES ─┬───────────────────────────────────┬───┘ └── STORAGE LIMIT NN ┬──────────┬───┘ └─ PERCENT ┘ ►─┬────────────────────────┬─────────────────────────────────────────────────► └─ DATASPACE ─┬─ NO ◄──┬─┘ └─ YES ──┘ ►─┬──────────────────────────────────┬───────────────────────────────────────►◄ └─ SHARED CACHE ─┬─ cache-name ──┬─┘ ├─ NULL ────────┤ └─ DEFAULT ◄────┘
Expansion of
area-override-specification
►►─┬───────────────┬─ physical AREA segment-name.area-name ──────────────────► ├─┬─ ADD ◄────┬─┤ │ └─ INClude ─┘ │ └─┬─ DROP ────┬─┘ └─ EXClude ─┘ ►─┬──────────────────────────────────────────────────────────────────┬──────► └─ MEMORY CACHE ┬──NO ◄───────────────────────────────────────┬────┘ └─ YES ─┬───────────────────────────────────┬─┘ └── STORAGE LIMIT NN ┬──────────┬───┘ └─ PERCENT ┘ ►─┬────────────────────────────────────────────────────────┬────────────────► └─ PAGE RESERVE size reserve-character-count characters ─┘ ►─┬──────────────────────────────────────────────────────┬──────────────────► └─ ON STARTUP SET STATUS TO ─┬─ UPDATE ◄─────────────┬─┘ ├─ RETRIEVAL ───────────┤ ├─ TRANSIENT RETRIEVAL ─┤ └─ OFFLINE ─────────────┘ ►─┬──────────────────────────────────────────────────────────────┬──────────► └─ ON WARMSTART ─┬─ MAINTAIN CURRENT STATUS ◄────────────────┬─┘ └─ SET STATUS TO ─┬─ UPDATE ──────────────┬─┘ ├─ RETRIEVAL ───────────┤ ├─ TRANSIENT RETRIEVAL ─┤ └─ OFFLINE ─────────────┘ ►─┬─────────────────────────────────┬───────────────────────────────────────►◄ └─ DATA SHARING ─┬─ NO ────────┬──┘ ├─ YES ───────┤ └─ DEFAULT ◄──┘
Parameters
CREATE/DROP DMCL
  • dmcl-name
    Names the DMCL. Dmcl-name is a 1- to 8-character name assigned according to naming conventions described in 7.3, "Naming Conventions".
ALTER DMCL
  • DEFAULT BUFFER
    buffer-name
    Specifies the default buffer for the DMCL. Buffer-name must identify a database buffer defined in the dictionary and associated with the DMCL.
    The default buffer is used for all files, unless overridden at the segment or file level.
    Native VSAM:
    For more information about assigning buffers for native VSAM files, see the "Usage" topic in this section.
    • NULL
      On an ALTER DMCL statement, removes the named buffer as the default buffer for the DMCL.
  • DBTABLE
    dbtable-name
    Specifies the name of the database name table to be used with the DMCL at runtime.
    • NULL
      Disassociates the database name table from the DMCL.
  • DATA SHARING
    data-sharing-attribute
    Specifies or removes attributes associated with data sharing operations.
    • NO
      —Removes data sharing-related information from the DMCL
    • data-sharing-attribute
      —Adds or changes the specified data sharing attribute
    Data sharing attributes apply to any DC/UCF system that uses this DMCL and is a member of a data sharing group. If data sharing attributes are not included in the DMCL of a CA IDMS system that becomes a member of a data sharing group, the following defaults will be used:
    • lock-entry-count: 4096
    • member-count: 7
    • default-cache-name: null
    • connectivity loss:
      NOABEND
Expansion of
data-sharing-attributes
  • LOCK ENTRIES
    lock-entry-count
    Specifies the number of lock table entries that will be allocated within the coupling facility lock structure. The value specified must be in the range 4096 through 1,073,741,824. The number of lock entries will be rounded up to a power of 2.
    • MEMBERS
      member-count
      Specifies the maximum number of CA IDMS systems that can be members of the system's data sharing group. The value specified must be in the range 7 through 247.
    • DEFAULT SHARED CACHE
      default-cache-name
      Specifies the default shared cache for any system using this DMCL. Default-cache-name must identify an XES cache structure defined to a coupling facility accessible to the CA IDMS system.
      The default shared cache for a system is used at runtime for any file whose area is designated as shared, if the file does not have an assigned cache. This value has no affect on files that are not associated with a shared area.
    • ON CONNECTIVITY LOSS
      Specifies what action the CA IDMS system is to take when either a loss in connectivity to or a failure of a critical coupling facility structure associated with a data sharing group is detected.
      • ABEND
        —Specifies that the CA IDMS system is to abnormally terminate immediately.
      • NOABEND
        —Specifies that the CA IDMS is to remain active in order to service non-data sharing-related requests.
      NOABEND is the default if ON CONNECTIVITY LOSS is not specified.
  • MEMORY CACHE
    Indicates global options for caching files in memory.
    For more information about operating-specific considerations in using memory cache and 64-bit storage, see the CA IDMS System Operations topics.
    • LOCATION
      Indicates where to allocate the storage for memory cache:
      • ANYWHERE
        Memory cache storage is allocated from 64-bit storage; if no or not enough 64-bit storage is available, dataspace storage is acquired.
      • 64 BIT ONLY
        Memory cache storage is allocated from 64-bit storage; if no or not enough 64-bit storage is available, memory caching fails.
    • STORAGE LIMIT
      Controls the amount of storage used for memory caching:
      • OPSYS
        Memory cache storage can be acquired until the operating system limit is reached. For 64-bit storage, the operating system limit is set through the MEMLIMIT parameter; for dataspace storage, the limit is optionally imposed by an operating system exit.
      • nnn MB, GB, TB, PB, EB
        CA IDMS controls the amount of memory cache storage if the value specified is smaller than the operating system limit. nnn must be a positive value between 1 and 32767. MB, GB, TB, PB, EB indicate the unit in which nnn is expressed. The abbreviations stand for Mega Byte (2**20), Giga Byte (2**30), Tera Byte (2**40), Peta Byte (2**50), and Exa Byte (2**60).
Expansion of
segment-specification
On an ALTER DMCL statement, specifies the name of a segment to be added to the DMCL, or identifies a segment in the DMCL to be altered or removed.
  • ADD
    Adds the named segment to the DMCL definition or alters its attributes.
  • DROP
    Drops the named segment from the DMCL definition.
  • SEGMENT
    segment-name
    Identifies the segment. Segment-name is a 1- to 8-character value that identifies a segment defined to the dictionary.
  • DEFAULT BUFFER
    buffer-name
    Specifies the buffer to be used by files associated with the segment. Buffer-name must identify a buffer associated with the DMCL. Unless overridden by a file override clause, all files associated with the segment will use the named buffer.
    Native VSAM:
    For information about assigning buffers for native VSAM files, see the "Usage" topic in this section.
  • NULL
    Removes the default buffer associated with the segment.
  • ON STARTUP SET STATUS TO
    Specifies the default startup status for areas associated with the segment. The startup status determines how CA IDMS/DB accesses an area when the DC/UCF system is started after an orderly shutdown.
    The status of an area determines the ready modes in which programs executing under the central version can obtain access to the area.
  • UPDATE
    Sets the status of the area to update and places an external lock on the area.
    When the status of an area is update, transactions executing under the central version can obtain access to the area in any ready mode.
    ON STARTUP SET STATUS TO UPDATE is the default when you do not include the ON STARTUP parameter in a CREATE SEGMENT statement.
  • RETRIEVAL
    Sets the status of the area to retrieval.
    When the status of an area is retrieval, transactions executing under the central version can obtain access to the area in retrieval modes only (that is, transient retrieval, shared retrieval, protected retrieval, and exclusive retrieval).
  • TRANSIENT RETRIEVAL
    Sets the status of the area to transient retrieval.
    When the status of an area is transient retrieval, transactions executing under the central version can obtain access to the area only in retrieval ready modes, and regardless of the ready mode, no record or row locks will be acquired.
  • OFFLINE
    Places the area offline.
    When the status of an area is offline, transactions executing under the central version cannot obtain access to the area in any ready mode.
  • ON WARMSTART
    Specifies the default warmstart status for areas associated with the segment. The warmstart status determines how CA IDMS/DB accesses an area when the DC/UCF system is started up after an abnormal termination.
  • MAINTAIN CURRENT STATUS
    Sets the area status to that in effect at the time the DC/UCF system was abnormally terminated.
    ON WARMSTART MAINTAIN CURRENT STATUS is the default when you do not include the ON WARMSTART parameter in a CREATE SEGMENT statement.
  • DEFAULT SHARED CACHE
    Specifies or removes the default shared cache for a segment.
    • default-cache-name
      —Specifies the name of the shared cache to be used for files associated with the segment. Default-cache-name must identify an XES cache structure defined to a coupling facility accessible to the CA IDMS system.
    • NULL
      —Removes the default shared cache from the segment.
    NULL
    is the default if DEFAULT SHARED CACHE is not specified.
    The value established at the segment level may be overridden at the file level.
  • DATA SHARING
    Specifies whether or not areas associated with the segment are eligible to be concurrently updated by CA IDMS systems that are members of a data sharing group.
    • YES
      —Specifies that concurrent update is allowed.
    • NO
      —Specifies that concurrent update is not allowed.
    NO is the default if DATA SHARING is not specified.
    The value established at the segment level may be overridden for individual areas within the segment.
Expansion of
file-override-specification
On an ALTER DMCL statement, specifies override attributes for a file in a segment that has been added to the DMCL.
  • ADD
    Adds or modifies file override information in the DMCL. ADD is the default.
  • DROP
    Drops file override information from the DMCL.
    This parameter does not drop file definitions from the DMCL.
  • segment-name.file-name
    Identifies the file whose attributes are being overridden. Segment-name must identify a segment included in the DMCL. File-name must identify a file in the named segment.
  • BUFFER
    buffer-name
    Specifies the buffer for the file. Buffer-name must identify a buffer associated with the DMCL.
    If no buffer is specified on a file override, the default buffer for the segment is used.
    Native VSAM: For information about assigning buffers for native VSAM files, see the "Usage" topic in this section.
  • DEFAULT
    Specifies that the file is to use the segment's default buffer. If the segment lacks a default buffer assignment, the default buffer is the default buffer assigned to the DMCL. DEFAULT is the default.
  • ASSIGN TO
    Associates the database file with an external file name that overrides the external file name assigned on a CREATE or ALTER FILE statement. All external file names in a DMCL definition must be unique.
  • ddname
    Specifies the external name for the file under z/OS or z/VM. Ddname must be a 1- through 8-character value that follows operating system conventions for ddnames.
  • filename
    Specifies the external name for the file under z/VSE. Filename must be a 1- through 7-character value that follows operating system conventions for filenames.
  • DEFAULT
    Removes the external file name override assigned to the file and re-assigns the external file name specified on a CREATE or ALTER FILE statement.
  • NULL
    Removes any external file name for the file. If you specify NULL, you must specify the data set name on the DSNAME clause and/or z/VM VIRTUAL ADDRESS clause of the FILE statement. This option is not valid under z/VSE unless DYNAM/D is being used.
  • DISP
    For z/OS and z/VM systems, specifies the disposition to be assigned when the file is dynamically allocated.
  • SHR
    Indicates that the data set specified on the DSNAME parameter will be available to multiple DC/UCF systems and local mode transactions at a time.
    Under z/VM, DISP SHR causes a link with an access mode of multiple read (MR).
  • OLD
    Indicates that the data set specified on the DSNAME parameter will be available to only one DC/UCF system or local mode transaction at a time.
    Under z/VM, DISP OLD causes a link with an access mode of multiple write (MW).
  • MEMORY CACHE
    Specifies whether or not to cache the file in memory.
    Note:
    When specified on the area override statement, this option applies to all files in the area. When specified on both the area and file override, the file override is used.
    • NO
        Specifies not to cache the file in memory.
      Note:
      This is the default for SYSTRK files and cannot be changed.
    • YES
        Specifies to limit the amount of 64-bit storage allocated for a given file to a percentage of a total file size, instead of allocating storage for the entire file.
      • STORAGE LIMIT NN PERCENT
        Specifies, in percentage, how much of the area's file to cache in memory.
        Limit:
        0 through 100
        • The value 0 or 100 specifies to cache the entire file in memory
        • The values 1 to 99 specify to limit the amount of 64-bit storage allocated for a given file to a percentage of a total file size, instead of allocating storage for the entire file.
    For more information about operating-system specific considerations in using memory cache and 64-bit storage, see the CA IDMS System Operations topics.
  • DATASPACE NO
    Same as MEMORY CACHE NO. This syntax is provided for upward compatibility only.
  • DATASPACE YES
    Same as MEMORY CACHE YES. This syntax is provided for upward compatibility only.
  • SHARED CACHE
    Specifies or removes the shared cache for a file.
    • cache-name
      —Specifies the name of the shared cache to be used for the file. Cache-name must identify an XES cache structure defined to a coupling facility accessible to the CA IDMS system.
    • NULL
      —Removes the shared cache assigned to the file.
    • DEFAULT
      —Specifies that the default cache specified for the segment will be used for the file.
    DEFAULT is the default if SHARED CACHE is not specified.
Expansion of area-override-specification
On an ALTER DMCL statement, specifies override attributes for an area in a segment that has been added to the DMCL.
  • ADD
    Adds or modifies area override information in the DMCL. ADD is the default.
  • DROP
    Drops area override information from the DMCL.
    This parameter does not drop area definitions from the DMCL.
  • segment-name.area-name
    Identifies the area whose attributes are being overridden. Segment-name must identify a segment included in the DMCL. Area-name must identify an area in the named segment.
  • MEMORY CACHE
    Specifies whether or not to cache the file in memory.
    Note:
    When specified on the area override statement, this option applies to all files in the area. When specified on both the area and file override, the file override is used.
    • NO
        Specifies not to cache the file in memory.
      Note:
      This is the default for SYSTRK files and cannot be changed.
    • YES
        Specifies to limit the amount of 64-bit storage allocated for a given file to a percentage of a total file size, instead of allocating storage for the entire file.
      • STORAGE LIMIT NN PERCENT
        Specifies, in percentage, how much of the area's file to cache in memory.
        Limit:
        0 through 100
        • The value 0 or 100 specifies to cache the entire file in memory
        • The values 1 to 99 specify to limit the amount of 64-bit storage allocated for a given file to a percentage of a total file size, instead of allocating storage for the entire file.
    For more information about operating-system specific considerations in using memory cache and 64-bit storage, see the CA IDMS System Operations topics.
  • PAGE RESERVE SIZE
    reserve-character-count
    Specifies the number of bytes to be reserved on each page to accommodate increases in the length of record occurrences or rows stored on the page. This clause overrides the value specified in the PAGE RESERVE SIZE clause of a CREATE or ALTER AREA statement.
    Reserve-character-count must be either 0 or a multiple of 4 in the range 48 through 32,716 and must be less than or equal to the area's page size. The default is 0.
    Native VSAM:
    For areas defined for native VSAM files, reserve-character-count must be 0.
  • ON STARTUP SET STATUS TO
    Specifies a startup status for the area that overrides the startup status specified for the segment with which the area is associated. See above for a description of this clause and its options.
  • ON WARMSTART
    Specifies a warmstart status for the area that overrides the warmstart status specified for the segment with which the area is associated. See above for a description of this clause and its options.
  • DATA SHARING
    Specifies whether or not the area is eligible to be concurrently updated by CA IDMS systems that are members of a data sharing group.
    • YES
      —Specifies that concurrent update is allowed.
    • NO
      —Specifies that concurrent update is not allowed.
    • DEFAULT
      —Specifies that the data sharing attribute of the segment will apply to the area.
    DEFAULT is the default if DATA SHARING is not specified.
  • FOR
    Specifies the operating system for which the DMCL is being generated. If not specified, the default is the operating system in which the GENERATE statement is executed.
  • MVS
    Generates a DMCL load module for the z/OS operating system.
  • VSE
    Generates a DMCL load module for the z/VSE operating system.
  • VM
    Generates a DMCL load module for the z/VM operating system.
  • dmcl-load-module-name
    Specifies the name of the DMCL load module to delete from the DDLCATLOD area.
  • PERMANENT
    Physically erases the DMCL load module. By default, CA IDMS/DB logically erases the DMCL load module and physically erases it upon system startup.
  • AREas
    On DISPLAY/PUNCH requests, identifies all database areas defined to the DMCL which have override specifications.
  • BUFfers
    On DISPLAY/PUNCH requests, identifies all database buffers and journal buffers associated with the DMCL.
  • FILes
    On DISPLAY/PUNCH requests, identifies all files defined to the DMCL which have override specifications.
  • JOUrnals
    On DISPLAY/PUNCH requests, identifies all disk, tape, and archive journal files associated with the DMCL.
  • SEGments
    On DISPLAY/PUNCH requests, identifies all segments contained in the DMCL.
  • DETails
    Displays or punches details about the DMCL.
  • HIStory
    Displays or punches:
    • The user who defined the DMCL
    • The user who last updated the DMCL
    • The date the DMCL was created
    • The date the DMCL was last updated
  • ALL
    Displays or punches all information about the DMCL. ALL is the default action for a DISPLAY or PUNCH verb.
  • NONe
    Displays or punches the name of the DMCL.
Usage
Ordering Definitions
You must define one or more database buffers for the DMCL before you add segments.
Assigning Buffers for Native VSAM Files
The following restrictions apply to buffers assigned to native VSAM files:
  • If the buffer is defined as NSR, all files using it must be associated with a single area.
  • If the file access method is KSDS, ESDS, PATH, or RRDS, then the associated buffer must be defined as NSR or LSR. Likewise, if the buffer is defined as NSR or LSR, only KSDS, ESDS, PATH, and RRDS files can use it
  • All PATH files associated with an area mapped to a KSDS or ESDS file must use the same buffer as the KSDS or ESDS file.
Assigning Buffers for Other Files
The page size of the buffer must be greater than or equal to the page size of all areas whose files are assigned to the buffer. If the file's access method is VSAM, the page size of the buffer must be greater than or equal to the file's control interval size.
External File Name
All non-blank external file names, including those for both database and journal files, must be unique within a DMCL. If necessary, use file overrides to assign unique names.
An external file name must be specified unless dynamic allocation will be used to access the file.
 For more information about dynamic file allocation in various operating systems, see 7.14.3, “Usage".
Archive Journal Block Size
Upon generation, the block size associated with an archive journal is checked to ensure it is not less than the block size of the disk journals. Since the block size of the disk journals is derived from the page size of the journal buffer, if the archive journal's block size is less than the page size of the journal buffer, the page size of the journal buffer is used and a warning message issued.
Caching Files in Memory
You can reduce retrieval I/O operations by caching a file in memory using the MEMORY CACHE clause of the file override specification. File caching is not supported for native VSAM files.
For more information about using memory caching, see Reducing I/O.
Dataspace Versus Memory Cache
The MEMORY CACHE clause replaces the use of the DATASPACE clause. The latter is still accepted for upward compatibility, but is no longer generated on displays.
Controlling Memory Cache
Use the DMCL-wide MEMORY CACHE options to control where and how much memory cache storage can be allocated.
Insufficient Storage for Memory Cache
If MEMORY CACHE YES is specified for a file, and not enough storage is available to cache the file in memory, processing continues as if MEMORY CACHE NO was specified.
Dynamically Changing Memory Cache Specification
The MEMORY CACHE specification can be changed dynamically:
  • Use DCMT VARY DMCL to change DMCL-wide MEMORY CACHE options
  • Use DCMT VARY FILE to change the MEMORY CACHE specification for a file.
 For more information about DCMT VARY DMCL and DCMT VARY FILE, see the CA IDMS System Tasks and Operator Commands topics.
Specifying Data Sharing Attributes
Each data sharing group has an associated coupling facility lock structure. The first CA IDMS system to become a member of the group, establishes the attributes of the lock structure. These attributes remain in effect until all members of the group have terminated normally. As long as any CA IDMS system is either active or has failed and not yet been restarted, the existing lock structure attributes remain in effect. Lock structure attributes include the number of lock entries and the maximum number of members. Both of these attributes affect the size requirements for the lock structure and should be chosen carefully.
 For more information about specifying data sharing attributes, see 24.4, “Reducing I/O”. Also see the CA IDMS System Operations topics.
Examples
Creating a DMCL
The following statement creates DMCL IDMSDMCL:
create dmcl idmsdmcl;
Assigning Buffers
The following statement assigns buffers to files associated with the DMCL:
  • File INDX_FILE in segment EMPSEG uses INDX_BUFF as its buffer
  • All other files in segment EMPSEG use EMP_BUFF as their buffer
  • All files in other segments in the DMCL use the default buffer
alter dmcl idmsdmcl default buffer def_buff add segment projseg add segment empseg default buffer emp_buff file empseg.indx_file buffer indx_buff add segment payseg;
More Information