Here's my SELECT-SQL query:

SELECT HistContact.PK_HistContact, HistContact.FK_HistRec;
    FROM HistContact;
    INNER JOIN HistRec ON HistRec.PK_HistRec == HistContact.FK_HistRec;
    INNER JOIN HistFile ON HistFile.PK_HistFile == HistRec.FK_HistFile;
    INNER JOIN HistDocket ON HistDocket.PK_HistDocket == HistFile.FK_HistDocket;
    WHERE (HistContact.FCC == "ABARJ329395001") AND (HistDocket.Docket == "9999") AND (HistFile.OutputType == "M")

Table HistContact have indexes on those fields:
- FK_HistRec
- FCC

Table HistRec have indexes on those fields:
- PK_HistRec
- FK_HistFile

Table HistFile have indexes on those fields:
- PK_HistFile
- FK_HistDocket
- OutputType

Table HistDocket have indexes on those fields:
- PK_HistDocket
- Docket

Here's the output of SYS (3054, 11):

Using index tag Fcc to rushmore optimize table histcontact
Rushmore optimization level for table histcontact: partial
Rushmore optimization level for table histrec: none
Using index tag Outputtype to rushmore optimize table histfile
Rushmore optimization level for table histfile: partial
Using index tag Docket to rushmore optimize table histdocket
Rushmore optimization level for table histdocket: partial
Joining table histdocket and table histfile using index tag Fk_histdoc
Joining table histcontact and table histrec using index tag Pk_histrec
Joining intermediate result and intermediate result using temp index

I guess the partial optimisation from tables HistContact, HistFile and HistContact is because I have no DELETED () index on these tables and it's OK.

HistRec show no optimisation and I guess it's OK since I have no conditions on this table. It's only part of the join clause.

What bother me is the last line:

Joining intermediate result and intermediate result using temp index

Why it's not using the indexes PK_HistFile and FK_HistFile to join the tables HistFile and HistRec?

Is there any way I can optimise further this query?

TIA