L command code

You can use the L command code to retrieve the last occurrence of a particular segment type or to insert a segment as the last occurrence of a segment type.

Retrieving a segment as the last occurrence

The L command code indicates that you want to retrieve the last segment occurrence that satisfies the SSA, or that you want to insert the segment occurrence you are supplying as the last occurrence of that segment type. Like F, L simplifies your programming because you can go directly to the last occurrence of a segment type without having to examine the previous occurrences with program logic, if you know that it is the last segment occurrence that you want. L can be used with GU or GHU, because IMS normally returns the first occurrence when you use a GU call. IMS disregards L at the root level.

Using L with GU, GN, and GNP indicates to IMS that you want the last occurrence of the segment type that satisfies the qualification you have provided. The qualification is the segment type or the qualification statement of the SSA. If you have supplied just the segment type (an unqualified SSA), IMS retrieves the last occurrence of this segment type under its parent.

For example, suppose you have this request using the medical hierarchy:

What was the illness that brought Jennifer Thompson, patient number 10345, to the clinic most recently?

In this example, assume that RULES=LAST is specified in the DBD for the database on ILLNESS. Issue this call to retrieve this information:

GU    PATIENTb(PATNObbb=b10345)
      ILLNESSb*L

The first SSA gives IMS the number of the particular patient. The second SSA asks for the last occurrence (in this case, the first occurrence chronologically) of the ILLNESS segment for this patient.

Inserting a segment as the last occurrence

Use L with ISRT only when the segment has no key or a non-unique key, and the insert rule for the segment is either FIRST or HERE. Using the L command code overrides both FIRST and HERE for HDAM or PHDAM root segments and dependent segments in any type of database.

Using the L command code to override the RULES specification on the DBD applies only to the path (either logical or physical) that you are using to access the segment for the ISRT call. For example, if you are using the physical path to access the segment, the command code applies to the physical path but not to the logical path. For clarification of using command codes with the RULES specification, ask your database administrator.