Unload function

Writes database segment data to a sequential output file.

The Unload function writes database segment data to a sequential output file. It can be used as part of a database reorganization, for unloading a database prior to changing the DBD definition, or to create a flat file of database segment data for other purposes.

Syntax - Command Line

mfims imsdbu UNLO {database-name|filename}
     [[NO]CLS] 
     [[NO]COMPRESS[(program)]]
     [DATA(position)]
     [DSN(filespec)]
     [ECHO(keyword,msglvl,stoplvl
     [[NO]INI(filespec)]
     [LAYOUT(type)]
     [[NO]LIST(filespec)]
     [LISTOPEN(disp)]
     [[NO]LOG(filespec)]
     [LRECL(length)]
     [PROGRESS(no-of-segments)]
     [RECFM(format)]
     [[NO]SEGEXIT[(program)]]
     [SEGM(position)]

Syntax - JCL

//UNLOAD EXEC PGM=MFDBUJCL,PARM='UNLOAD,database-name,{dataset-name | catalog-name}'
//SYSOUT    DD SYSOUT=* 
//OUTPUT    DD DSN=output-dataset,DISP=SHR

Parameters - Command Line

database-name
The name of a database on which the function operates.
filename
The name of a file containing a list of databases on which the function operates.
CLS
Clears the screen before starting the utility. NOCLS prevents the initial clear screen and can be helpful when you are running a series of utilities in a command file.
Default: NOCLS
COMPRESS
Enables or disables the expansion of the input data file records.
Default: NOCOMPRESS
Sub-parameter
program The name of a compression/expansion routine to use instead of the system-supplied routine.
Syntax Rules
  1. Use COMPRESS only when LAYOUT(G) is specified. COMPRESS is not required and is ignored when LAYOUT(D), LAYOUT(I) or LAYOUT(S) is specified.
  2. Specifying COMPRESS with no program name causes decompression using the CBLDCIMS program (built into the MFIMS software libraries). You can override the name of the compression/expansion routine by specifying a user-written program name.
General Rules
  1. When using an Unload file for a subsequent Load, the COMPRESS directive used for unloading must also be used when loading. For the IMSDBU-specific LAYOUT(D) formats, this is automatic as the compression setting is stored in the unload file header record. For generic format unloads, ensure that the COMPRESS directive is set correctly to avoid data corruption.
DSN
Specifies the dataset name of the input file containing the segment data.
Default: DSN(*.DBU)
Sub-parameter
filespec The dataset name of the output for the segment data.
Syntax Rules
  1. If you specify the base name of filespec as an asterisk (*) it is replaced by the DBD name.
  2. Use unique extensions for the output file names. This is enforced even if the database data files are in a different directory than the output file.
  3. The output dataset resides in the current directory unless you specify a drive and/or directory.
  4. The output file name, not including the drive and directory, must not be the same as the name of the files for the database. For example, the data files for a database named MYDBD would be MYDBD.DAT and MYDBD.IDX, and the output file name cannot be either of these file names.
ECHO
Controls the display of and interaction with the messages displayed by IMSDBU.
Default: ECHO(MSGS,4,8)
Sub-parameters
keyword The category of information displayed. One of the following:
ALL
Always displays processing messages, input source or detail information and the ending message. Warning and error messages are displayed and stop for user input if the message level is equal to or greater than the msglvl and stoplvl values.
MSGS
Always displays processing messages and the ending message. No source or detail information is displayed. Warning and error messages are displayed and stop for user input if the message level is equal to or greater than the msglvl and stoplvl values.
ERREND
Always displays the utility ending message. Warning and error messages are displayed and stop for user input if the message level is equal to or greater than the msglvl and stoplvl values.
ENDMSG
Displays ending message only if the utility ending return code is equal to or greater than msglvl. A "Press any key to continue" message is displayed and stops for input if the utility ending return code is equal to or greater than the stoplvl. Enter a msglvl and/or stoplvl value of zero to display and/or stop on every ending message.
COND
Both the warning/error and ending messages are conditional on the msglvl and stoplvl values. Warning and error messages are displayed and stop for user input if the message level is equal to or greater than the msglvl and stoplvl values. The ending message is displayed if the ending return code is equal to or greater than msglvl. You see the message "Press any key to continue" which requires input if the utility ending return code is equal to or greater than the stoplvl.
ERRORS
You see warning and error messages which require input if the message level is equal to or greater than the msglvl and stoplvl. You do not see the ending message.
msglvl A value from 4 through 20 to indicate the severity of messages to display.1
stoplvl A value from 4 through 20 to indicate the severity of messages to stop for user input. 1
1 Can take the following values:
Value Category Example Cause
4 General warning message A minor coding error in DBD source which DBDGEN can make an assumption about and continue.
6 IMS specific warning message A warning that a keyword or statement is not supported and is ignored - processing can continue.
8 General severe error An incorrect coding in DBD source which cannot be compensated for, such as 'no DBD statement'.
10 IMS Option specific severe error An unsupported feature was defined which cannot be compensated for, such as 'Exceeded some maximum'.
12 Severe error - possible temporary condition A temporary I/O error such as a 'file locked' or 'database locked' status.
16 Severe error- permanent - likely installation problem A permanent I/O error, such as an invalid data set name or member name, was input to a utility or an environment variable is not set correctly.
20 Severe error - permanent An unrecoverable I/O error or some other unexpected error.
INI
Specifies the default directives file.
Default: None
Sub-parameter
filespec The name and location of the .INI file containing directives that override the IMSDBU programmed defaults.
Syntax Rules
  1. filespec can include a drive and/or directory if required. If you do not specify a drive or directory, IMSDBU looks for the named .INI file in the current directory.
  2. Directives listed in the .INI file override the IMSDBU programmed defaults.
  3. Directives entered on the command line or interactive screen override directives in the .INI file.
  4. Specifying NOINI prevents any .INI file from overriding the programmed defaults.
  5. If you specify an .INI file that does not exist, the programmed default directives are used as if NOINI were specified.
General Rules
  1. An .INI file is an ASCII text file containing a heading, [IMSDBU] on line 1, starting in column 1, followed by a list of mfims imsdbu directives; one directive per line. A line is terminated by a return or an end-of-file. Comment lines are indicated by an asterisk (*) or semi-colon (;) in column 1. For example: 
    [IMSDBU]
PROGRESS(1000)
;use local log
LOG(C:\MYDIR\MYDB.LOG)
LAYOUT
Specifies the type of the input or output file.
Default: LAYOUT(D)
Sub-parameter
type The type of output file. One of:
D
The output file is an IMSDBU file layout. No additional directives are required to describe the input file.
G
The output file is a generic layout. Additional directives are required to describe the input file and its contents.
I
The output file is an IBM format. No additional directives are required to describe the input file.
S
The output file is a sequential file. Additional directives are required to describe the input file and its contents.
Syntax Rules
  1. The additional directives required for the G and S parameters are RECFM, LRECL, SEGM, and DATA.
General Rules
  1. LAYOUT(I) output files are not suitable for uploading to the mainframe and reloading IMS/ESA databases.
  2. LAYOUT(I) automatically sets the directives RECFM(V), LRECL(0), SEGM(7), DATA(36) and NOCOMPRESS.
LIST
Controls the location and name of the detail listing file, which includes items such as source listings, completion status, error messages and execution statistics.
Default: LIST(*.LST)
Sub-parameter
filespec The name and location to use for the listing file.
Syntax Rules
  1. filespec can include a drive and/or directory if required. If you do not specify a drive or directory, IMSDBU creates the listing file in the current directory.
  2. NOLIST suppresses the creation of the listing file.
  3. To specify a path, you can use the convention of placing a dollar sign ($) in front of the name of an environment variable that represents a path. For example, LIST($ENVVAR\*.DOC) creates a list file of dbdname.DOC in the directory named by the ENVVAR environment variable.
  4. Specifying LIST(*.LST) or LIST(*.RPT) causes the listing file to be created in the project listing directory.
  5. If no path is specified, the listing file is created in the current directory.
  6. If you specify the base name of filespec as an asterisk (*), it is replaced by the DBD name; this allows IMSDBU to provide separate reports for functions that can operate on multiple databases. It also assists in maintaining historical detailed reports by DBD name.
  7. Specifying LIST with no filespec is equivalent to specifying LIST(*.LST).
LISTOPEN
Controls the open disposition of the detail listing file.
Default: LISTOPEN(NEW)
Sub-parameter
disp The disposition to use. One of:
NEW
Creates a new listing file or overwrites an existing one.
MOD
Appends the list output to an existing file or creates a new listing if one does not exist. MOD allows you to maintain a detailed historical record of database functions.
Syntax Rules
  1. LISTOPEN is ignored when NOLIST is specified.
LOG
Specifies the IMSDBU activity log, which shows the ending message status for each function.
Default: LOG(IMSDBU.LOG)
Sub-parameter
filespec The name and location of the file to use as the IMSDBU activity log.
Syntax Rules
  1. filespec can include a drive and/or directory if required. If you do not specify a drive or directory, the listing is created in the current directory.
  2. Specifying NOLOG suppresses the log file output.
General Rules
  1. The log file is created if it does not exist.
  2. The log file is historical with the most recent entries written to the end of the file.
  3. As the log file grows in size over time, it might require deletion periodically.
LRECL
Specifies the length for fixed length generic layout output records.
Default: LRECL(0)
Sub-parameter
length The length for fixed length generic layout output records.
Syntax Rules
  1. LRECL is required when loading from a fixed-length generic file; that is, when LAYOUT(G) is specified.
  2. LRECL is not required and is ignored when LAYOUT(D), LAYOUT(I) or LAYOUT(S) is specified.
  3. LRECL(0) causes IMSDBU to assign the smallest possible value. The value used will appear in the detail report listing.
PROGRESS
Controls the frequency of progress reporting.
Default: PROGRESS(200)
Sub-parameter
no-of-segments A value between 0 and 9999 indicating the number of segments to process before displaying a progress message. 0 disables progress reporting.
Syntax Rules
  1. We recommend that you do not reduce the number of segments specified to a value below its default of 200. Very small values measurably reduce the performance of the database function.
  2. For relatively fast systems, setting the value higher (such as to 1000 or larger) might improve performance slightly.
General Rules
  1. The progress message could show the number of segments processed, or the percentage complete and an estimate of the time remaining.
RECFM
Specifies the format of the input or output records.
Default: RECFM(V)
Sub-parameter
format The format of the input records. One of:
V
Records are variable length. With LAYOUT(G), each record is prefixed with a 2-byte record length (LL) and the file is in the same format as created by the VRECGEN utility. With LAYOUT(S), files are in Micro Focus record sequential format.
F
Records are a fixed length.
U
Records are unformatted.
Syntax Rules
  1. RECFM is not required and is ignored when LAYOUT(I) is specified.
  2. When format is set to V and LAYOUT(G) is specified, each record is prefixed with a 2-byte record length (LL) and the file is in the same format as created by the VRECGEN utility.
  3. When format is set to V and LAYOUT(S) is specified, files are in Micro Focus record sequential format.
  4. When format is set to F, you must also specify LRECL to provide the record length.
SEGEXIT
Specifies the name of a user-supplied exit program that can be used to control selection and modification of segment data during the add process.
Default: NOSEGEXIT
Sub-parameter
program The name of the exit program to use.
Syntax Rules
  1. NOSEGEXIT disables this exit.
SEGM
Specifies the starting position of the 8-byte segment name in the data record.
Default: SEGM(1)
Sub-parameter
position The starting position of the 8-byte segment name in the data record.
Syntax Rules
  1. A value of 1 corresponds to the first byte of the record data.
  2. Use the SEGM directive only when LAYOUT(G) or LAYOUT(S) is specified.
  3. SEGM is not required and is ignored when LAYOUT(D) or LAYOUT(I) is specified.
  4. When RECFM(V) is specified, the variable length record prefix (LL) is not considered part of the record data and does not affect this value. That is, if the segment name is the first field following the LL field in a variable length file, specify 1 for the SEGM value.
General Rules
  1. When loading GSAM files, the SEGM value is ignored.
  2. When loading Fast Path databases which use LTERM keys (related or non-related), the SEGM directive indicates the position of the LTERM name and not the segment name.

Parameters - JCL

database-name
The name of a database on which the function operates.
dataset-name
Dataset name of the data to be unloaded.
catalog-name
If the dataset containing the data to be unloaded is in the JCL catalog, then you can specify the catalog name instead of the dataset name.
output-dataset
The dataset containing output data.

Input

The database to be unloaded must be a primary physical DBD or GSAM DBD which has been defined using DBDGEN. The data files for secondary index databases are not required by Unload. When unloading databases containing logical children, the database files for the logical parents is not required. An error message will result if you attempt to unload one of the following databases:

  • The primary index for a HIDAM database.
  • Secondary index databases. If you need to extract 'user data' from a secondary index, you can use the DBUTIL utility or develop your own program.
  • Databases defined as ACCESS=LOGICAL. IMSDBU manages logical relationships using the physical databases. If you need to unload data using a logical DBD, you can use the DBUTIL utility or develop your own program.

User Exit program Database Catalog types cannot be unloaded by IMSDBU. Unload is supported for single-user exclusive use databases and shared read-only databases. The DBUTIL utility can unload User Exit databases.

Output

There is a variety of output file formats supported for unloading databases. See the Specialized and Generic Load Inputs of the IMS Database Utility (IMSDBU) topic for complete details of the different formats. Any of the formats supported by the Load function can be created using Unload.

Parent topic: mfims imsdbu functions
Related concepts
IMSDBU Exits
IMS and GSAM Databases
IMS Database Utility (IMSDBU)
Related reference
MFDBUJCL Utility
COMPRESS
DATA
DSN
LAYOUT
LRECL
RECFM
SEGEXIT
SEGM