SQLEXEC on each new trail file or just on replicat start to capture current FILESEQNO?

Question

Dear community,
I need to capture fileseqno of the trail file that replicat is processing. But I only need to capture it once without overhead of adding fileseqno column to target tables.
I clearly understand that using colmap ( usedefaults, FILESEQNO = @GETENV ("RECORD", "FILESEQNO") ) inserts fileseqno value for every record captured from logs, but what I'm trying to accomplish is to react on the event of changing fileseqno number while replicat is running.
Following application logic I actually only need to capture fileseqno of the first trail, that is processed by replicat.
What I've tried so far is using following parameters for replicat (given two tables to be replicated):
table m.EventHead,
sqlexec( id set_first_seq_no1, spname pk_replication_accounting.set_first_seq_no, params( a_fileseqno = @GETENV( "GGFILEHEADER", "FILESEQNO" ) ), afterfilter ),
filter (@coltest( set_first_seq_no1.a_fileseqno, NULL ) or @coltest( set_first_seq_no1.a_fileseqno, MISSING ) or @coltest( set_first_seq_no1.a_fileseqno, INVALID ) ),
eventactions( ignore record );
table m.EventTail,
sqlexec( id set_first_seq_no2, spname pk_replication_accounting.set_first_seq_no, params( a_fileseqno = @GETENV( "GGFILEHEADER", "FILESEQNO" ) ), afterfilter ),
filter (@coltest( set_first_seq_no2.a_fileseqno, NULL ) or @coltest( set_first_seq_no2.a_fileseqno, MISSING ) or @coltest( set_first_seq_no2.a_fileseqno, INVALID ) ),
eventactions( ignore record );
pk_replication_accounting.set_first_seq_no is defined within package as
procedure set_first_seq_no( a_fileseqno in out pls_integer );
With filter clause I've tried to instruct GG to perform SQLEXEC only for the first record captured for every table, but with no success. Stored procedure is fired multiple times upon every record in trail file.
As far as I understand standalone SQLEXEC is not capable of obtaining value of @GETENV( "GGFILEHEADER", "FILESEQNO" ), though I have not tried it yet.
Another way, that I see, is to instruct extract to add one fake record for every new trail file and then to process it within map clause with SQLEXEC. For example if SOURCEISTABLE had per table effect, then we could get our single record for every trail using dual table:
sourceistable
table dual;
Still I don't know how to achieve required behavior.
Please help, if you know some workarounds.

Answer 1

Managed to capture current fileseqno for every replicat start with following parameters:
ignoreupdatebefores
map m.EventHead, target gg.tmp_gg_dummy, handlecollisions, colmap ( id = @GETENV ("RECORD", "FILERBA") )
sqlexec( id set_first_seq_no1, spname pk_replication_accounting.set_first_seq_no, params(a_fileseqno = @GETENV( "GGFILEHEADER", "FILESEQNO" ) ), afterfilter ),
filter (@getenv( "STATS", "TABLE", "GG.TMP_GG_DUMMY", "DML" ) = 0), insertallrecords;
map m.EventTail, target gg.tmp_gg_dummy, handlecollisions, colmap ( id = @GETENV ("RECORD", "FILERBA") )
sqlexec( id set_first_seq_no2, spname pk_replication_accounting.set_first_seq_no, params(a_fileseqno = @GETENV( "GGFILEHEADER", "FILESEQNO" ) ), afterfilter ),
filter (@getenv( "STATS", "TABLE", "GG.TMP_GG_DUMMY", "DML" ) = 0), insertallrecords;
tmp_gg_dummy is defined as the following:
create global temporary table gg.tmp_gg_dummy ( id number( 14, 0 ) ) on commit delete rows;
alter table gg.tmp_gg_dummy add constraint tmp_gg_dummy_pk primary key ( id );
Procedure is fired only once per every replicat start and report file shows the following:
From Table m.EventHead to GG.TMP_GG_DUMMY:
  Stored procedure set_first_seq_no1:
         attempts:         0
       successful:         0
From Table m.EventTail to GG.TMP_GG_DUMMY:
       #                   inserts:         0
       #                   updates:         1
       #                   deletes:         0
       #                  discards:         0
  Stored procedure set_first_seq_no2:
         attempts:         1
       successful:         1
though original mapping from m.EventTail has
inserts:   
69
updates:   
21
befores:   
21
deletes:    
0
discards:    
0