Processing Matching Records

Matching records for two or more files are processed in the following manner:

Whenever a record from the primary file matches a record from the secondary file, the primary file is processed first. Then the matching secondary file is processed. The record identifying indicator that identifies the record type just selected is on at the time the record is processed. This indicator is often used to control the type of processing that takes place.
Whenever records from ascending files do not match, the record having the lowest match field content is processed first. Whenever records from descending files do not match, the record having the highest match field content is processed first.
A record type that has no match field specification is processed immediately after the record it follows. The MR indicator is off. If this record type is first in the file, it is processed first even if it is not in the primary file.
The matching of records makes it possible to enter data from primary records into their matching secondary records because the primary record is processed before the matching secondary record. However, the transfer of data from secondary records to matching primary records can be done only when look-ahead fields are specified.

Figure 47 through Figure 48 show how records from three files are selected for processing.

Figure 47. Normal Record Selection from Three Disk Files

The records from the three disk files above are selected in the order indicated by the dark numbers.

Table 30. Normal Record Selection from Three Disk Files
Cycle	File Processed	Indicators On	Reason for Setting Indicator
1	PRIMARY	02	No match field specified
2	PRIMARY	02	No match field specified
3	FIRSTSEC	04	No match field specified
4	SECSEC	05	Second secondary low; no primary match
5	PRIMARY	01, MR	Primary matches first secondary
6	PRIMARY	01, MR	Primary matches first secondary
7	FIRSTSEC	03, MR	First secondary matches primary
8	FIRSTSEC	03	First secondary low; no primary match
9	FIRSTSEC	03	First secondary low; no primary match
10	SECSEC	05	Second secondary low; no primary match
11	PRIMARY	01	Primary low; no secondary match
12	PRIMARY	01, MR	Primary matches second secondary
13	PRIMARY	02	No match field specified
14	SECSEC	05, MR	Second secondary matches primary
15	SECSEC	05, MR	Second secondary matches primary
16	SECSEC	06	No match field specified
17	PRIMARY	01, MR	Primary matches both secondary files
18	FIRSTSEC	03, MR	First secondary matches primary
19	FIRSTSEC	04	No match field specified
20	SECSEC	05, MR	Second secondary matches primary
21	FIRSTSEC	03	First secondary low; no primary match
22	PRIMARY	01, MR	Primary matches both secondary files
23	FIRSTSEC	03, MR	First secondary matches primary
24	FIRSTSEC	02, MR	First secondary matches primary
25	SECSEC	05, MR	Second secondary matches primary
26	SECSEC	05, MR	Second secondary matches primary

Figure 48. Normal Record Selection from Three Disk Files

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