Extract data layout

The data extracted from IMS is written to a flat file, with the following layout characteristics:

Header record

The header stores information required by FM/IMS when reloading the data. It comes in two formats: a Dynamic PSB header record; and a Static PSB header record:

Dynamic PSB header record

This record is the first line in the extract file, and has the following format:

Table 1. Dynamic PSB header record structure

Columns	Field	Description
1-8	Sort field	All columns set to low values (x'00'), so that when the file is sorted, the header record remains the first record
9-15	Product code	Set to "FM/IMS"
16-25	Version number	Set to current FM/IMS version
26	Reserved
27-28	Extract record prefix length	This is calculated in the extract record format as x=33+max_ckeylen-1
29-30	Maximum concatenated key length
31-46	Date/time	Date and time that the extract file was created
47	EOR	End of record - reserved

Static PSB header record(s)

When using a Static PSB in the extract process, the header records created may span several lines. They are distinguished from the segment records by having 0 in the logical order number field (column 1-2). The first header record has the format:

Table 2. Static PSB first header record structure

Columns	Field	Description
1-9	Sort field	All columns set to low values (x'00'), so that when the file is sorted, the header record remains the first record (this is one byte longer than the sort field in the Dynamic header record)
10-16	Product code	Set to "FM/IMS"
17-26	Version number	Set to current FM/IMS version
27	Reserved
28-29	Extract record prefix length	This is calculated in the extract record format as x=34+max_ckeylen-1
30-31	Maximum concatenated key length
32-47	Date/time	Date and time that the extract file was created
48-59	PSB Type	Set to "STATIC PSB"
60-73	Index	If the PSB did not use a secondary index, this field is blank. Otherwise, it is the word "INDEX", followed by the DBD name of the index.
74	EOR	End of record - reserved

After the first header record, a Static PSB extract has additional header records to store information about the PSB used during the extract. Each record includes the list of SENSEGs for each of the databases included in the extract. These records have the format:

Table 3. Static PSB subsequent header record structure

Columns	Field	Description
1-2	Sort field	All columns set to low values (x'00'), so that when the file is sorted, the header record remains the first record
3-4	Header sequence number	To order the additional header records during sort
5-8	Reserved	Set to low values (x'00')
9-16	Header DBD name	DBD of one of the databases involved in the extract
17-??	SENSEG list	Variable length; 8 bytes per senseg

IMS segment record

The IMS segment records have the following format:

Table 4. IMS segment record structure

Columns	Field	Description
1-2	Logical number order	Used to sort the file, so logical children are inserted after logical parents. This is "01" for normal segments, "02" for logical children and either dependent segments.
3-4	Database number	The PCB number used to extract the data, for logical relationships the primary database specified on the Extract panel has a value of 1. Logically related databases have a value of 2, 3, and so on.
5-8	Extract order	Order in which the IMS segments were extracted by FM/IMS
9-16	DBD name	DBD of one of the databases involved in the extract
17-18	Segment code
19-26	Segment name
27-28	Reserved	Set to low values (x'00')
29-32	Concatenated key length	Actual concatenated key length for this segment
33-??	Concatenated key
??-??	IMS segment data	This starts at 33+Max concatenated key length