while starting extract in 4 node rac db it ws abending with below error

GGSCI (oel603 as ggadmin@TROY_3) 2> start extract E1

Sending START request to MANAGER ...
EXTRACT E1 starting

erro message

2020-08-26T09:13:07.923+0100  INFO    OGG-06604  Oracle GoldenGate Capture for Oracle, e1.prm:  Database TROY CPU info: CPU Count 2, CPU Core Count 12, CPU Socket Count 2.
2020-08-26T09:13:08.161+0100  INFO    OGG-03522  Oracle GoldenGate Capture for Oracle, e1.prm:  Setting session time zone to source database time zone 'Europe/London'.
2020-08-26T09:13:12.158+0100  INFO    OGG-01971  Oracle GoldenGate Capture for Oracle, e1.prm:  The previous message, 'INFO OGG-03522', repeated 5 times.
2020-08-26T09:13:12.158+0100  INFO    OGG-02089  Oracle GoldenGate Capture for Oracle, e1.prm:  Source redo compatibility version is: 11.2.0.0.0.
2020-08-26T09:13:12.175+0100  INFO    OGG-00546  Oracle GoldenGate Capture for Oracle, e1.prm:  Default thread stack size: 10485760.
2020-08-26T09:13:12.191+0100  INFO    OGG-01515  Oracle GoldenGate Capture for Oracle, e1.prm:  Positioning to begin time 2020 M08 26 07:31:22.
2020-08-26T09:13:18.019+0100  INFO    OGG-01516  Oracle GoldenGate Capture for Oracle, e1.prm:  Positioned to (Thread 1) Sequence 158076, RBA 16656384, SCN 0.0 (0), 2020 M08 26 07:31:22.
2020-08-26T09:13:18.019+0100  INFO    OGG-01515  Oracle GoldenGate Capture for Oracle, e1.prm:  Positioning to begin time 2020 M08 26 07:31:22.
2020-08-26T09:13:27.348+0100  INFO    OGG-01516  Oracle GoldenGate Capture for Oracle, e1.prm:  Positioned to (Thread 6) Sequence 34003, RBA 28048912, SCN 0.0 (0), 2020 M08 26 07:31:22.
2020-08-26T09:13:27.348+0100  INFO    OGG-01515  Oracle GoldenGate Capture for Oracle, e1.prm:  Positioning to begin time 2020 M08 26 07:31:22.
2020-08-26T09:13:35.053+0100  INFO    OGG-01516  Oracle GoldenGate Capture for Oracle, e1.prm:  Positioned to (Thread 2) Sequence 160452, RBA 21640208, SCN 0.0 (0), 2020 M08 26 07:31:22.
2020-08-26T09:13:35.053+0100  INFO    OGG-01515  Oracle GoldenGate Capture for Oracle, e1.prm:  Positioning to begin time 2020 M08 26 07:31:22.
2020-08-26T09:13:59.092+0100  ERROR   OGG-00446  Oracle GoldenGate Capture for Oracle, e1.prm:  error retrieving redo log sequence for begin time 2020-08-26 07:31:22.000000Not able to establish initial position for begin time 2020-08-26 07:31:22.000000.
2020-08-26T09:13:59.093+0100  ERROR   OGG-01668  Oracle GoldenGate Capture for Oracle, e1.prm:  PROCESS ABENDING.

check threads in you db

SQL> select inst_id,INSTANCE_NAME,HOST_NAME,THREAD# from gv$instance;

   INST_ID INSTANCE_NAME    HOST_NAME                                                           THREAD#
---------- ---------------- ---------------------------------------------------------------- ----------
         3 TROY_3       oel603                                                                1
         1 TROY_1       oel604                                                                3
         4 TROY_4       oel607                                                                6
         2 TROY_2       oel608                                                                2

but distinct thread showing as 1,2,3,4,5,6

 SQL> select distinct thread# from v$thread;

   THREAD#
----------
         1
         6
         2
         4
         5
         3

so add this in your extract paraeter file so that only 1,3,6,2 threads are used 

TRANLOGOPTIONS DBLOGREADER
THREADOPTIONS PROCESSTHREADS SELECT 1
THREADOPTIONS PROCESSTHREADS SELECT 3
THREADOPTIONS PROCESSTHREADS SELECT 6
THREADOPTIONS PROCESSTHREADS SELECT 2

now you should be able to start the extract