IAM CREATE Override Statement Format

Specifies the DD name of the IAM data set that the override is to be applied to. Up to 40 DD names may be specified. If multiple DD names are specified they must be enclosed in parenthesis and separated by commas.

DD=&ALLDD will result in this override being applied as a global override to all IAM files being defined, loaded or re-cataloged in this step, unless otherwise explicitly overridden.

When used during an IDCAMS DEFINE, it is recommended that DD=&ALLDD or the DSN= keyword be used. If using the DD= override for a define process, the value must match the value specified for the FILE (ddname) keyword on the IDCAMS DEFINE control statement. In this circumstance, there is no need for the actual DD statement as specified by FILE (ddname) or DDNAME= on the CREATE override to be present in the JCL.

An * as the last character of the specified DDNAME indicates that only the characters up to but not including the * should be used to match the actual DDNAMEs used in this step. This wildcard allows a single override to be applied to more than one DDNAME, based on its name. Do not specify DD=* to reference all DDNAMEs in the job. Use DD=&ALLDD to do this.

There is no default. Either DDNAME or DSN must be specified.

Specifies the data set name of the IAM data set that the override is to be applied to. One data set name per override control statement is permitted.

An * as the last character of the specified DSN indicates that only the characters up to but not including the * should be used to match the actual data set names used in this step. This wildcard allows a single override to be applied to more than one DSN, based on its name.

There is no default. Either DDNAME or DSN must be specified.

Specifies that the input data is in IAM Data Compressed format. The Backup Compressed option is only valid for IAM software compressed data sets. It is ignored for hardware compressed data sets. It can only be specified on a file load step with data that was created with the IAM ACCESS Override of BACKUPCOMPRESSED. Specification of this option forces the output file to have a data compressed format.

Default is that data is treated as standard, uncompressed data.

Specifies a blocking factor or an explicit block size for the IAM file. For values from 1 to 15, IAM will use a block size that will result in the specified number of blocks per track for the device type on which the data set is being allocated to. For values of 300 or larger, IAM will use that value as an explicit block size. Values from 16 to 299 are invalid.

Default is generally 4 blocks per track, based on the IAM Global Option VSAMBLOCKF, the default blocking factor for IAM files defined under the VSAM interface. A larger block size may be used however if the DEFINE indicates a larger value for a Control Interval Size, or fewer than 5 records will fit in the default block size.

Specifies the buffering option to be used for the file load. Because the file load is essentially a sequential output process, the buffering is different than the normal IAM Real Time Tuning Buffering. The MINBUFNO and MAXBUFNO values are not used during the file load. During the file load, IAM acquires a number of buffers based on this parameter. When half of the buffers are filled with data they are written out to the device in a single I/O operation. When the second group of buffers is filled, IAM will wait for the prior I/O to complete, then start the I/O for the second group, and let the application begin filling up the first group of buffers. The buffers are requested from extended private storage. This keyword value is only utilized for a file load step; it is ignored for define. The values that can be specified are:

BSAM - Use the BSAM Access Method macros to load the file. The default number of buffers is 12, unless overridden by the BUFNO override. These buffers are all acquired in below the line storage.

CYL - Buffers for one cylinder's worth of blocks is acquired, approximately 1/2 cylinder is written per I/O.

MCYL - Buffers for two cylinder's worth of blocks is acquired, one cylinder is written per I/O. For Encrypted data sets, which infers that a VSAM Linear Data set will be used, two Control Area’s worth of blocks is acquired and one Control Area is written per I/O.

MTRK - Buffers for ten tracks are acquired, five are written per I/O.

TRK - Buffers for two tracks are acquired, one track is written per I/O.

64BIT - Same buffering as MCYL except with 64-bit virtual storage used for the buffers.

Default value is MCYL, or as otherwise specified in the IAM Global Options Table.

Specifies whether or not IAM is to attempt to compress the data content of each record. Valid values are YES, NO, HW, HARDWARE, SW, or SOFTWARE.

Specifying YES will enable the use of IAM data compression. The type of data compression used, software or hardware, will be set based on the IAM Global Options Table, which defaults to Software. This will usually result in significant savings of DASD space for the file, reduce virtual storage requirements to process the file, and reduce physical I/O (EXCP's) for the file. Files must have at least 10 bytes of data after the key to be eligible for data compression. If the IAM data compression does not reduce the size of a record, it is placed in the file uncompressed.

Specifying NO will result in all of the data records being stored in the file without IAM performing any data compression.

Specifying HW, HWE or HARDWARE will use the hardware compression instruction. This type of compression requires a compression dictionary. IAM will either dynamically build one during file load, or the user can create a compression dictionary and specify the name using the DICTIONARY override. In either case, the dictionary will be stored within the loaded data set. Specification of HWE will use the enhanced hardware dictionary build process to identify additional data patterns that may improve the amount of data compression achieved. Customers may be able to achieve greater compression through the use of the hardware compression facility, particularly if they pre-build a compression dictionary using the CSRBDICT REXX exec, which is a more complex dictionary build process. Hardware compression should not be used on processors prior to the IBM Z family due to the significant CPU overhead on the older processors. The hardware compression overhead has been substantially reduced on the IBM Z processors, and may in some circumstances use less CPU time than the IAM software compression.

Specifying SW or SOFTWARE will cause IAM to use its internal software compression technique that does not require a dictionary.

Default is files that are defined with a primary space of 75 tracks (5 cylinders) or larger will automatically be eligible for IAM data compression, and will default to software. This file size and compression technique can be changed in the IAM Global Options Table. The size limitation is ignored when the override is specified.

Specifies the size, in megabytes, of the Data Space to be used for the temporary storage of the index to the IAM file that is being loaded. This override is ignored during file definition. Valid values are from 0 to 2048. A value of 0 results in the use of a dynamically allocated temporary data set, or other data set that may be specified via the WKDDNAME override and DD card.

Default value is 2048 megabytes, or as otherwise specified in the IAM Global Options Table.

Specifies the four-character suffix for the name of the user provided hardware compression dictionary. The dictionary must be in load module format, with the first four characters being ‘IAMD’, and the second four characters will be the customer’s choice. Review Using-Hardware-Compression on Hardware Compression for information on creating and naming the compression dictionaries.

Default is to use a dictionary dynamically created by IAM during the file load when hardware compression has been requested.

Specifies the external IAM file format on DASD, and is only valid for customers using z/OS 1.7 or above.

LARGE indicates that the IAM file should be an MVS Large Format Sequential DataSset.

EXT indicates that the IAM file should be a DFSMS Extended Format file.

BASIC indicates that the IAM file should be a standard PS data set.

Default is determined by the Global Options.

For use when the IAM Global Option of ENABLE=VAM is set to force dynamic allocation instead of the DADSM SVC allocation that is used with the CA Allocate (formerly VAM) product.

Specifies that IAM is to create this file in the Enhanced format. Enhanced format KSDS files offer various processing enhancements including the ability to dynamically acquire additional DASD space for updates and inserts that occur after the file is loaded. The use of Enhanced format files is required for IAM ESDS and RRDS files, for IAM files that have an alternate index, or forIAM files that will be used with the IAM RLS facility.

Default is Enhanced format file, unless otherwise specified in the IAM Global Options Table.

Specifies the journal records that IAM will write to the log stream for non-CICS file processing that is identified by the LOGSTREAM parameter. This override is only used on recatalog requests to alter prior values that the data set was defined with. Values that can be specified are:

ALL Specifies that both undo and redo records will be generated.

NONE Specifies that no records will be generated.

REDO Specifies that redo records will be generated that enables users to reapply the updates such as in a forward recovery process.

UNDO Specifies that undo records will be generated that enables users to remove updates in a back out recovery process.

Default is no journal records will be written to the log stream unless the file was defined with the FRLOG parameter or the LOGREPLICATE parameter.

Specifies whether or not IAM will use z/HPF architecture on devices that are capable of utilizing that function. Specifying YES will cause IAM to use z/HPF architecture on the volumes that the system indicates are capable of supporting EXCP processing with z/HPF commands. Specifying NO indicates that IAM will not use the z/HPF architecture I/O commands.

Default is YES that z/HPF will be used unless otherwise specified in the IAM Global Options Table.

Specifies whether or not the file is eligible for a compressed index. Valid values are YES, LONG or NO.

When YES is specified, the file still has to meet the minimum size requirement as indicated by Global Options which defaults to 8000 bytes. The key length must be between 4 and 128, and the index compression must yield storage savings of at least 10%.

When LONG is specified, IAM will use a Long Key Compression algorithm, which does not limit a compression set size to 256 bytes. This will provide index compression for files with keys longer than 128 bytes, and may also provide other files with keys of 32 bytes or longer with better compression.

When NO is specified, a compressed index will not be created for the file. For files with high random I/O activity, or with a very large number of records being randomly inserted into the file, not using the compressed index may reduce CPU time, at the expense of potentially substantial increased virtual storage requirements.

Default value is YES except for files with keys of 33 bytes or more which will default to LONG.

Specifies the amount of space, as a percentage, that is to be reserved for future growth within each prime data block during file load. This field is identical to the VSAM CI free space parameter. This value is also used for prime extension blocks as records are being added to the logical end of the file. Valid values are from 0 to 99. For most files the use of a large value for CI free space is counter-productive in that it results in a lot of unused space within the file.

Default, for KSDS files, is from the CI FREESPACE value specified during the file define. For ESDS and RRDS files, the default is 0 or as otherwise specified in the IAM Global Options Table for ESDSINTEGRATED or RRDSCI%.

Indicates that the type of journaling, if any, that IAM will perform. When specified on the CREATE override, either during file definition or file load, the journaling specification will be used for any file update operation. Journaling can also be overridden by an IAM ACCESS override statement.

For files not being processed by IAM/RLS or IAM/PLEX, users must pre-allocate and catalog a log data set to be used for the journaling, which is required to be the name of the IAM data set / cluster, appended with the characters “.LOG”. IAM journaling will not be active during file loads, reorganizations, or during recovery from the journal.

For files being processed by IAM/RLS or IAM/PLEX, the users must specify the journal data sets to the IAM/RLS or IAM/PLEX startup procedure.

One of the following values can be specified:

BOTH - The IAM log data set will contain both before and after images. This will enable the user to perform either a forward recovery, or a backward (backout) type of recovery.

BEFORE - The IAM log data set will contain only before images of updated records. This option allows backwards (backout) recoveries only.

AFTER - The IAM log data set will contain only the after images of updated records. This option allows forward recoveries only.

NONE - The IAM journaling feature will not be used for this IAM data set.

Default value is NONE.

Indicates whether or not the IAM Override processor is to display this override card on the job log. Valid values are YES or NO. This is not recommended for use with the REREAD option, particularly on CICS regions or for IAMRLS, as it can result in significant output to the job log and system log.

Default value is NO; the override is not displayed unless it is in error.

Specifies that IAM will generate replication journal records to the log stream identified by the LOGSTREAM parameter. This is for use with the IAM DEFINE RECATALOG process only as a way to alter the originally specified value.

Specifies the name of the system logger log stream that is to be used for the journal records requested by the LOGREPLICATE or FRLOG parameters. This override is used only so that the log stream name can be changed as part of the IAM DEFINE RECATALOG process.

Specifies the maximum number of buffers IAM will acquire during file processing when BUF64 is enabled. If MAX64BUF is coded on an CREATE Override Statement it will override the MAXBUFNO setting when 64-bit buffer storage is being used for IAM buffers. Either the IAM Global Option BUF64 must be enabled or BUF64=YES must be used on an ACCESS Override statement for this CREATE Override to have an affect. This allows the user to set a much higher maximum buffer value when 64-bit buffers are in use and to have a lower value (MAXBUFNO) when 64-bit buffer storage is not in use. There is no default value since MAXBUFNO will be used, if MAX64BUF is not coded. The maximum value that can be coded is 99999999 (9,999,999) but the amount of 64-bit addressable virtual storage that is available in an address space will be a limiting factor.

Specifies the maximum number of buffers IAM will acquire during file processing. IAM's Real Time Tuning dynamically adjusts the number of buffers used for a file as I/O demands change, up to the limit specified or defaults to for MAXBUFNO. While this has no effect during the file load, the value is saved within the file, and will be used as a default value for the file when opened for input or update processing. Valid values are from 0 to 24576.

A value of 0 indicates no override value for MAXBUFNO is set. This can be used with a DEFINE RECATALOG to nullify any previous setting of MAXBUFNO.

Default is 0, that no maximum number of buffers will be associated directly with the file itself; IAM Global Options and Access Options will control the maximum number of buffers.

Specifies a multiplication factor to be used by the IAM Dynamic Secondary Space Adjustment feature. Once a file has five or more extents on a volume, the secondary space value will be increased by the MAXSECONDARY factor, unless it exceeds the primary space value or the amount of space available on the volume. Valid values are from 0 to 25. A value of 0 will disable this feature. MAXSECONDARY is ignored on DFSMS Extended Format files due to the large number of extents that they can take per volume.

During the IAM file Define process, if the IAM Global Option SPACEADJ is set to Enabled and the SMSEXTOK option is set to disabled, then the initial IAM define data set allocation will have the primary and secondary values multiplied by this MAXSECONDARY value. No five extents volume adjustment will then be done later. See the Space Adjustment subsection earlier in this section for additional details.

Default value is 10 during file define or load, unless otherwise specified in the IAM Global Options table.

Specifies the minimum number of buffers IAM will acquire during file processing when BUF64 is enabled. If MIN64BUF is coded on a CREATE Override statement it will override the MINBUFNO setting when 64-bit buffer storage is being used for IAM buffers. Either the IAM Global Option BUF64 must be enabled or BUF64=YES must be used on an ACCESS Override statement for this CREATE Override to have an affect. This allows the user to set a much higher minimum buffer value when 64-bit buffers are in use and to have a lower value (MINBUFNO) when 64-bit buffer storage is not in use. The MIN64BUF value coded must be lower than or equal to the MAX64BUF value. MIN64BUF can be used to have an entire IAM file brought into virtual storage. If MIN64BUF is set to a value that is equal to or higher than the number of blocks in the file (prime data, overflow data, and PE blocks) then an entire file can reside in 64-bit addressable virtual storage. If MIN64BUF is set to a number that is greater than what's needed for the entire file to be in virtual storage, IAM will make sure the actual number of buffers is not greater than the number of blocks in the data set to avoid wasting virtual storage.

Specifies the minimum number of buffers that IAM will maintain during file processing. IAM's Real Time Tuning dynamically adjusts the number of buffers used for a file as I/O demands change, but will never use less than the specified or defaulted value for MINBUFNO. Valid values are from 0 to 24576. Specifying an equivalent number of buffers for MAXBUFNO will effectively disable IAM's Real Time Tuning algorithm. If MINBUFNO is overridden by a value greater than 0, then that value will be used as the initial number of buffers to acquire during Open processing. If the value for MINBUFNO is set larger than MAXBUFNO, it will be set down to the MAXBUFNO value.

A value of 0 indicates no override value for MINBUFNO is set. This can be used with a DEFINE RECATALOG to nullify any previous setting of MINBUFNO.

Default is 1 as a minimum number of buffers will be associated with the file.

Indicates whether IAM is to use the PRIMARY or SECONDARY space allocation value, when IAM anticipates that the next extent will be obtained on another DASD volume. Valid values are PRIMARY or SECONDARY. MULTIVOLUME is ignored for DFSMS Extended Format data sets due to the large number of extents they can take on each volume.

Default value is PRIMARY, based on the IAM Global Options Table.

Specifies that no log replication records will be written to the journal. This is only for use as part of the IAM DEFINE RECATALOG process to turn off a prior specification of LOGREPLICATE.

When specified for DEFINE or LOAD of an ESDS type of IAM file will result in an ESDS file with a standard 4-byte RBA. This is intended to be used to override defaults from the Global Options that would have the ESDS be an Extended Addressable format with an 8-byte RBA or with the IAM PSEUDORBA value. This will also override the Extended Addressable specification from the SMS Data Class.

Use the NOREUSE Create Override to either Define a new IAM Data set as NOREUSE or to switch an existing file from REUSE to NOREUSE, using an IDCAMS DEFINE CLUSTER RECATALOG job step.

Specification of PE=0 will circumvent normal VSAM rules by allowing a file to be loaded with 0 records. Standard VSAM requires at least one record to be inserted into a file before it is considered to be in the loaded state.

If PE=0 is specified and there are data records loaded into the file, then this will prevent IAM KSDS and RRDS files from having any prime extension blocks. This is intended for use on files where records are continuously being added to the logical end of the file (that would normally go into PE blocks) and are also deleting those records. Because PE space is not reusable this can result in files continuing to use more and more space. With the PE=0 specification, the records will instead be placed into overflow blocks which are reusable. The PRO format may also be advantageous for these type of files.

Default value is that PE blocks (prime extension) will be added to the file as needed based on records being logically added to the end of the file.

Indicates whether or not IAM should use the Prime Related Overflow structure. This format is only recommended for use on data sets that are subject to a large number of inserted records and are not shared for read only while being updated unless it is used under IAM/RLS or IAM/PLEX. Valid values are YES or NO. PRO files cannot be used with IAM Version 8.1 and earlier versions of  IAM.

The default is based on the value in the IAM Global Options Table which is shipped as NO.

Specifies that an IAM ESDS file can exceed 4 gigabytes in size, through the use of non-standard 4-byte RBAs (Relative Byte Addresses). If the application has dependencies on the RBA to be identical to VSAM, then this parameter must not be used. This is helpful for applications that exceed the 4-gigabyte data size, and would require changes to support an 8-byte RBA value.

Default is standard VSAM 4-byte RBA.

Specifies whether IAM is to release unused space after the file is loaded, or reorganized. By default, IAM will release unused space in a file's allocation after the initial load, providing that secondary space was specified.IAM will reserve some space, if any is available, of the over allocated space based on CA free space, or the Overflow override if it is specified. Valid values are:

YES -IAM will release unused, unreserved space after each load or reorganization.

NO - IAM will not release unused DASD space. This may be useful to hold on to DASD space for future expansion.

Default is to release unused, unreserved DASD space on the first load only, and only if a secondary space quantity has been specified. The default can be changed in the IAMGlobal Options Table.

Indicates that IAM will reread the overrides each time an IAM file is opened. This will be automatically done for CICS, IAM/RLS, and IAM/PLEX address spaces. If specified, this keyword should appear on all of the override cards supplied in the file. This is primarily intended to be used by long running jobs, where the IAMOVRID points to a sequential data set or PDS member. This provides a mechanism for users to change overrides, and have them take effect by closing and reopening the IAM files.

Default is that the IAM override parameters are once per job step and kept in storage except for CICS, IAM/RLS, and IAM/PLEX.

Use the REUSE Create Override on an IAM File IDCAMS DEFINE CLUSTER RECATALOG job step to switch an existing IAM file from NOREUSE to REUSE.

When specified with no operand on define or load, indicates that this data set is to be processed using IAM/RLS or IAM/PLEX, regardless of Share Options or the IAM RLS Data Set Name Tables. The operand, if specified, is the four character identifier of the IAM/RLS or IAM/PLEX address space that this data set is to be processed by.

When specified with no operand on a Define Recatalog process it will nullify any prior RLSID specification.

When loading an IAM RRDS file, specifies whether the RRDS is being loaded in ascending relative record number sequence, or in a random relative record number sequence. The values that can be specified are:

SEQUENTIAL – Specifies that the RRDS file is being loaded in ascending relative record number sequence. This is the default value for variable length record RRDS files. Use this override when loading a fixed length record RRDS file which is being loaded in ascending relative record number sequence when the program indicates random processing.

RANDOM – Specifies that the RRDS file is being loaded in a random relative record number order. This is the default value for fixed length RRDS files when the program indicates random processing. Specify this override to load a variable length record RRDS file in random relative record number sequence, which is a function not provided by VSAM. IAM will use data spaces to hold the records written until the file is closed. IAM will then sort the records within the data spaces, and write the records to the file in ascending record number sequence.

Default is RANDOM for fixed length record RRDS files, and SEQUENTIAL for variable length record RRDS files.

This value is only used for a Define Recatalog process. It provides a mechanism for changing the share option to a value different than what was specified when it was originally defined or last recataloged. Refer to Defining-IAM-Files for a description of the various Share Options. Valid values are 1, 2, 3, or 4.

Default is that the file will retain the current Share Option.

Activates the IAM request trace capability, and indicates where the trace data is to be written to. Normally, it is written to SYSOUT; however, it can also be written to a disk or tape file. To generate a printed report, specify a DD name of IAMTRPRx, where 'x' is any valid character. If 'x' is a 'C', then the key of each record is printed in character format, otherwise the key is printed in hexadecimal format.

Default is no trace output is produced.

For a file define request, specifies a generic unit name for non-specific volume allocation. Disk volumes associated with the specified generic name must be mounted as STORAGE, and the VOLUMES parameter must specify 'ANYVOL' to activate IAM's non-specific volume allocation. This feature cannot be used for DFSMS managed data sets, or for CA-Vantage Allocation Manager, formerly Sterling's SAMS (VAM) managed data sets.

Default is SYSDA, unless otherwise specified by the WORKUNIT field in the IAM Global Options Table.

Specifies whether or not IAM is to enable variable length record support for the overflow area. Once a file has variable overflow enabled, it will not be disabled without doing a reorganization. Valid values are YES or NO. Use of variable length overflow will for many files reduce the amount of DASD space used for the overflow area.

Default is YES, unless specified differently in the IAMGlobal Options Table.

Specifies the DD name of the DD statement specifying a temporary sequential data set used as temporary storage for the file’s index as it is being loaded. This is generally not needed, as IAM normally uses 64-bit virtual, a data space, or its own dynamically allocated temporary data set. However, for cases where the data space usage is not allowed, or cannot be large enough, and the default space allocation of the temporary work data set is insufficient, a user can provide their own data set allocation for this purpose.

A special value of 64 can be specified which will indicate that IAM is to use 64-bit virtual instead of the data space or a work file. This is useful if the WORK64 Global Option is disabled.

Default if using a work data set is IAMWKDD.

For ESDS type of files, enables the use of 8 byte RBA values. This will allow ESDS files to exceed the 4-gigabyte file size with compatibility to DFSMS. If the Extended Addressability option has been set in the DFSMS Data Class for this ESDS file, then 8-byte RBA support is automatic. This option must not be specified if PSEUDORBA has been specified.

Default value is based on the Extended Addressability from the SMS Data Class or from the IAM Global Options. If neither is set, then will default to a standard 4 byte RBA value.