IAM ACCESS 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 comas.

DD=&ALLDD will result in this override being applied as a global override to all IAM files being accessed in this step, unless otherwise explicitly overridden.

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.

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 data set name.

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

For files that are software compressed, specifies that IAM is not to decompress the data when passing it back to the requester. The data will be passed back to the requester in an IAM data compressed format. The data can be used for backup and reorganization purposes, but it is not usable by application programs. The data must be reloaded into an IAM file with the BACKUPCOMPRESSED IAM CREATE override specified, or the data must be decompressed with the IAMRECVR utility.

Default is that the data is returned in a normal, uncompressed format.

Specifies the maximum amount of storage that can be used for buffers, in kilobytes. If specified, this value will supersede any specification for MAXBUFNO. When specified, MAXBUFNO is computed as (BUFSPACE*1024)/BLOCKSIZE.

Default is BUFSP or CICSBUFSP from the IAM Global Options Table.

Specifies whether or not 64-bit virtual storage is to be used for the buffers. Valid values are YES or NO.

Default is NO for non-CICS address spaces unless the IAM Global Option for BUF64 has been changed. The default is YES for CICS address spaces unless the IAM Global Option for CICSBUF64 has been changed.

Indicates that IAM should utilize 64-bit addressable virtual storage as a cache area for extended overflow blocks. This may provide for faster sequential processing. Requires z/OS 1.4 and above. Users may have to specify the MEMLIMIT= JCL keyword on the EXEC card to provide 64-bit addressable storage.

Specified for selected files being used under IAM/RLS or IAM/PLEX for which consistent reads are required. Consistent reads will acquire the record lock to ensure that the caller retrieves the most current version of a record. This override is specified on IAM overrides for the IAM/RLS address space.

Specifies whether or not IAM will immediately write out updated buffers. Valid values are YES or NO. Specifying this will override the default for deferred writing, which is based on the share options the file was defined with, and whether or not the file is opened under CICS. Specifying YES will indicate that IAM will delay writing out an updated block until the buffer it resides in is required for another block, or until file close. Specifying NO will indicate that IAM will always immediately write out any updated data blocks.

Default is YES when a file has Share Option of 1 or 2, and is being accessed by a batch job. The default is NO when a file has Share Option of 3 or 4. For CICS, all randomly updated, inserted, or deleted records will cause an immediate write unless YES is specified. May also default to NO based upon the setting for the IMMEDWRITE IAM Global Option.

Specifies whether or not IAM/RLS and IAM/PLEX will perform Dynamic Job Backout processing for this job. Valid values are YES or NO. Specifying YES will indicate that IAM will backout any records changed by this job step for recoverable IAM files that are processed byIAM RLS should this job step abend. Specifying NO will indicate that the backout will not automatically occur; the user will have to use IAMJREST or other recovery process. Only files that have journaling of before images through IAM/RLS and IAM/PLEX will be recovered.

Default is the IAM/RLS and IAM/PLEX Dynamic Job Backout action specified on the IAM RLS startup parameters.

Specifies an amount of memory for IAM'S Dynamic Table. The value is specified in 1K (1024 byte) increments. IAM will attempt to GETMAIN the requested quantity during open, and if successful, will use that storage as a cache for randomly read records. On all random requests, where the complete key is specified, IAM will search the table for the record. These requests are identified on the IAMINFO report by GET RANDOM requests. If found, the record is returned without any physical I/O. If the record is not currently in the table, it will be read from disk, and placed in the table after it is retrieved.

Updates are always made both to the table and to the file. Variable length records are maintained as maximum length entries.

Valid values are from 0 to 16000 (that is, Dynamic Table up to 16,000K bytes). The storage is requested from extended private. This override cannot be used when DYNDS has been specified.

Default value is 0, the Dynamic Table is disabled.

Specifies the size of the IAM Dynamic Data Space in megabytes (MB). This override cannot be used when DYNCORE is specified. It provides a similar function to the DYNCORE feature, only an MVS Data Space is used instead of virtual storage from the users address space. This will allow for a larger area of storage to be used, with improvements in memory management over DYNCORE.

Valid values are from 32 to 2048.

Default value is 0.

For ESDS type of IAM files, specifies whether or not IAM will use CI locking for applications that are adding records to ESDS files. Valid values are YES or NO. Some applications that write multiple records to an ESDS type of file per transaction may have a requirement that all of those records are written consecutively without being intermixed with records being added by other transactions. That is confirmed by using the ESDS locking (ESDSLOCK=YES). If the application does not have that dependency, then turning off (ESDSLOCK=NO) this function may yield better performance.

Default is YES unless revised in IAM Global Options Table.

Specifying this option enables a second virtual storage index level for the IAM Overflow Index. If there is a lot of random I/O done (10s of thousands or greater) when there are many records in Overflow (100s of thousands or greater), having a 2nd level Overflow index can improve performance and save CPU time. EXPOVIX will be ignored for PRO format files because PRO format overflow files use a different Overflow Index structure.

Specifies the journal records that IAM will write to the log stream for non-CICS file processing that is identified by the LOGSTREAM parameter. 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.

The INDEXSPACE operand is no longer in use by IAM at IAM v10.0.01 and above. IAM will always use 64-bit virtual storage for the IAM File in the memory Index Area. INDEXSPACE can still be coded as on an ACCESS Override but it will be ignored. Please make sure that your system MEMLIMIT setting allows for the use of 64-bit storage for the IAM Index Area.

Specifies the IAM journaling capabilities to be used. If the value specified enables journaling, the value will be combined with any specification from the CREATE override when the file was defined or loaded.

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 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 and IAM/PLEX, the override MUST be provided on the IAM/RLS or IAM/PLEX address space and the users must specify the journal data sets to the IAM/RLS and IAM/PLEX startup procedure if they want to use journaling.

The ACCESS override only changes the journaling value for the job step on which it is specified. Valid values are:

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.

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

BEFORE - The IIAM log data set will contain before images of updated records. This option allows backward (backout) recoveries only. If AFTER images were specified on a CREATE override, then AFTER images will still be logged to the journal.

AFTER - The IAM log data set will contain after images of updated records. This option allows forward recoveries only. If BEFORE images were specified on a CREATE override they will still be logged to the journal.

NONE - The IAM journaling feature will not be used for the specified IAM data sets for this job step.

Default value is NONE, unless otherwise specified.

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

Default is that the override card is not displayed in the job messages, unless there is a syntax error on the override card.

Specifies that IAM will generate replication journal records to the log stream identified by the LOGSTREAM parameter. This will only be done by IAM for non-CICS application updates. Not intended for use with GDPS Active-Active which requires that the file be defined with this attribute.

Specifies the maximum number of buffers IAM will acquire during file processing when BUF64 is enabled. If MAX64BUF is coded on an ACCESS 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 the same ACCESS Override statement for this MAX64BUF ACCESS 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. Valid values are from 1 to 24576.

Default is based on the larger of MAXBUFNO or BUFSP, or for CICS the larger of MAXBUFNO or CICSBUFSP from the IAM Global Options Table. As shipped, the default is the number of buffers that will fit within 65,536K of virtual storage, except for CICS where the default is 16,384K. For a typical IAM file on a 3390, with quarter track blocking, the default MAXBUFNO is 4,904 except under CICS where it is 1149.

Specifies the maximum value, in megabytes, to which IAM Dynamic Region Adjustment will set the extended private region. This feature permits processing of files with large virtual storage requirements without the need to modify an installation's IEFUSI exit. Valid values are from 0 to 1024. A value of 0 will disable the Dynamic Region Adjustment feature.

Default value is 512 megabytes, or as otherwise specified in the IAM Global Options Table.

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, providing that it does not exceed 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. This is ignored for files in DFSMS Extended Format.

Default value is 5 during file access, or as 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 ACCESS 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 the same ACCESS Override statement for this MIN64BUF 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 1 to 24576. Specifying an equivalent number of buffers for MAXBUFNO will effectively disable IAM's Real Time Tuning algorithm. If MINBUFNO is overridden, then that value will be used as the initial number of buffers to acquire during Open processing. The MINBUFNO will be reduced to MAXBUFNO if the specified MINBUFNO value is larger than MAXBUFNO.

Default value is 1.

Keyword that specifies IAM can ignore the MEMLIMIT for 64-bit virtual storage for the index, if necessary, to prevent a failure. IAM will only do this when a request is failed due to MEMLIMIT being exceeded up to a limit of 64 gigabytes being used for the index.

Default is IAM abides by the MEMLIMIT, unless otherwise specified in the IAM Global Options Table.

Specifies that for Linear / Encrypted Data Sets, I/O buffers will be page fixed. Additionally, if use of 64-bit addressable virtual storage has been enabled (BUF64=YES or CICSBUF64=YES), then Large Memory 1 megabyte page frame sizes will be enabled if the z/OS system is configured to have Large Memory Page Frames available. When using 64-bit buffers, if Large Memory page frames are not available then standard 4K pages will be page fixed.

CPU usage will be slightly lower with this option enabled.

Sites that have sufficient real memory with generally low paging rates can enable this access option to minimize I/O response times for their most performance sensitive IAM encrypted files.

Specifies that IAM is not to use the IAM/RLS and IAM/PLEX services for the identified data sets.

Default action is based on IAM Global Options, and whether or not the IAM/RLS or IAM/PLEX address spaces are active.

Controls when the data set fragmentation is assessed and how often the REORG IS RECOMMENDED messages are issued

You can specify a number from 0 to 72 representing an interval of time in hours. Specifying 0 (the default value) triggers an assessment of the data set only during OPEN and CLOSE operations. Specifying a number from 1 to 72 triggers an assessment of the data set while it is being used between OPEN and CLOSE operations. This is done in addition to assessments during OPEN and CLOSE operations. If IAM determines that a reorganization is recommended, it issues the message REORG IS RECOMMENDED no more frequently than the specified interval. For example, if you set REORGTIME=24, the REORG IS RECOMMENDED message is issued daily. It might take longer than the specified interval for the repeated messages to appear, depending on the data set's I/O activity. 

Indicates that IAM will reread the overrides each time an IAM file is opened. This is automatically done for CICS, IAM/RLS, and IAM/PLEX address spaces. When used it is recommended that this keyword appear on all of the ACCESS 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 read when the first IAM file in a job step is opened, and kept in a table in virtual storage.

Indicates whether or not IAM is to re-read empty prime blocks when processing the file. When IAM is processing a file with REREADEMPTY=NO being specified or defaulted to, IAM will track the blocks that are detected as containing no data. Subsequent requests for those blocks will assume that they are empty, and therefore not do any I/O to read them. With REREADEMPTY=YES, IAM does not keep track of empty blocks, and will always read into storage the requested block.

Default action is based on the Cross Region Share Option, and the type of OPEN. For files defined with Share Option 1 opened for INPUT or UPDATE, and for files defined with Share Option 2 opened for UPDATE, the default is REREADEMPTY=NO. For all other cases, REREADEMPTY defaults to YES.

Specifies that IAM is to process this file using the IAM/RLS or IAM/PLEX services. If the IAM/RLS or IAM/PLEX services are not available, then the OPEN will be failed.

Default is based on the IAM Global Options and whether or not the IAM/RLS or IAM/PLEX address spaces are active.

Specifies the amount of storage to be used, as a multiplier factor to the block size, for the IAM/RLS and IAM/PLEX sequential fast path function. IAM will fill the specified amount of storage with as many records as will fit each time the request is made. Valid values are 0 – 8. A value of 0 will turn off the Sequential Fast Path processing.

Default value is 2, meaning that IAM will use a buffer area that is double the block size when the IAM/RLS or IAM/PLEX Fast Path function is used.

Specifies the four character identifier of the IAM/RLS or IAM/PLEX address space that is to be the host address space for this data set. This keyword is primarily intended to be used with a DD=&ALLDD override card, and then with any other override cards that are specified for that job step. Specification of an RLSID on the ACCESS override does not force a data set to be processed under IAM/RLS or IAM/PLEX, but rather directs it to an IAM/RLS or IAM/PLEX address space if IAM RLS processing is otherwise indicated for this data set.

Default value is the value of the IAM Global Option RLSID, which is shipped as RLS1.

Specifies the VSAM Cross Region Share Option to be used for this job step. This provides a mechanism for accessing the file with a different Share Option than it had been defined with. Share Options affects the ENQ that is done to protect the file from concurrent access, and will also impact the buffering for the file. Refer to the 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 be opened based on the Share Option specified when the file was defined.

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.

Specifies the type of tracing to be done.

TRALL - Activates all of the trace points.

TRIOS - Trace start of each logical I/O request.

TRIOE - Trace at end of each logical I/O request.

TRBFR - Trace internal IAM calls to the IAM Buffer Manager.

TREXCP - Trace physical I/O requests.

TRXTND - Trace file expansion (extend) calls.

TRDYN – Trace calls to the Dynamic Data Space.

TRINT -- Tracing is done to an internal table kept in 64bit virtual storage.

Multiple values for TRACEREQUEST can be specified by enclosing the desired keywords within parenthesis.

Default value is TRIOS.

Specifies whether or not IAM should modify its Real Time Tuning algorithms when heavy physical I/O is being performed in short time periods. Valid values are YES or NO.

The default value is YES, unless changed in the IAM Global Options Table. This global option is set via the ENABLE and DISABLE Global Options.

Overrides the ENQ processing that IAM will perform for the specified file. Normally, IAM will base the ENQ on the defined cross region share option. Valid values are:

EXCL - Indicates that IAM is to perform an exclusive ENQ on the file. This will prevent any other OPEN for this IAM file, within the scope of the ENQ capabilities provided on the host system.

SHR - Indicates that IAM is to perform a shared ENQ on the file. If specified for all users of the file, it will permit multiple jobs to have update capability to the same IAM file.

NONE - Prevents IAM from issuing any ENQ for the file being opened. The file will not be protected from concurrent update or even from a concurrent attempt to reload the file, while this application has the file open. This value should be specified when the file is being used by a job that is utilizing MVS Checkpoint / Restart facilities.

The default ENQ processing is based on the cross region share options, and the type of OPEN being issued for the data set.

Specifies whether or not IAM is to enable variable length record support for the overflow area. This override will only take effect when the file is opened for update. Once a file has variable overflow enabled, it cannot be turned off until the file is reorganized. Valid values are YES or NO.

Default is the value set when the file is defined or loaded, which defaults to YES, unless changed in the IAM Global Options Table.