Help me in reading/understanding Explain Plan

Question

Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
SELECT SRC2.PGM_MSTR_NBR,
                                              SRC2.PGM_TRK_NBR,
                                              SRC2.CNTL_LOCN,
                                              SRC2.PGM_NAME,
                                              SRC2.PGM_STS,
                                              SRC2.SIS_PGM_START_DATE,
                                              SRC2.SIS_PGM_END_DATE,
                                              SRC2.AWARD_TRGT,
                                              SRC2.AWARD_MAX,
                                              SRC2.COMPLNC_TYPE,
                                              SRC2.CMPNY_VNDR_LOCN,
                                              SRC2.CMPNY_VNDR_NBR,
                                              LKP3.ADDR_NAME,
                                              SRC2.INV_IND,
                                              SRC2.LAST_INV_THRU_DATE,
                                              SRC2.INV_RPT_DAY,
                                              SRC2.INV_RPT_CYCLE,
                                              SRC2.BEG_COLL_DATE,
                                              SRC2.END_COLL_DATE,
                                              SRC2.SLS_CONT_DIST,
                                              SRC2.SLS_CONT_NBR,
                                              SRC2.ORD_INV_START_DATE,
                                              SRC2.ORD_INV_END_DATE,
                                              SRC2.CMPLNC_RPT_IND,
                                              SRC2.PROD_ENTRY_LVL,
                                              SRC2.DIST_ENTRY_LVL,
                                              SRC2.CUST_ENTRY_LVL,
                                              SRC2.VNDR_ENTRY_LVL,
                                              SRC2.VNDR_CONT,
                                              SRC2.SIS_CMPNY_VNDR_NBR
                                              FROM CASADM.SBA_REB_PGM SRC2
                                              INNER JOIN(SELECT PGM_MSTR_NBR,PGM_TRK_NBR,CNTL_LOCN  FROM CASADM.ACCR_SIS_PURCH_DTL
                                                         UNION SELECT PGM_MSTR_NBR,PGM_TRK_NBR,CNTL_LOCN  FROM CASADM.ACCR_SIS_EXCL_DTL)ACCR2
                                                    ON  (SRC2.PGM_MSTR_NBR=ACCR2.PGM_MSTR_NBR AND SRC2.PGM_TRK_NBR=ACCR2.PGM_TRK_NBR AND SRC2.CNTL_LOCN=ACCR2.CNTL_LOCN)
                                              LEFT OUTER JOIN
                                                        CASADM.MT_CMPNY_VNDR LKP3
                                                    ON (LKP3.CMPNY_VNDR_NBR=SRC2.CMPNY_VNDR_NBR);
Record Count in each table:
select count(*) from casadm.accr_sis_purch_dtl --375,968
select count(*) from casadm.accr_sis_excl_dtl --1,988,867
select count(*) from casadm.sba_reb_pgm --526,133
select count(*) from casadm.mt_cmpny_vndr --20743
Execution Plan
Plan hash value: 1465316812
| Id  | Operation                    | Name                  | Rows  | Bytes |TempSpc| Cost (%CPU)| Time|
|   0 | SELECT STATEMENT             |                       |     9 |  1908 | | 26988   (2)| 00:06:18 |
|   1 |  NESTED LOOPS OUTER          |                       |     9 |  1908 | | 26988   (2)| 00:06:18 |
|*  2 |   HASH JOIN                  |                       |     9 |  1656 |83M| 26979   (2)| 00:06:18|
|   3 |    TABLE ACCESS FULL         | SBA_REB_PGM           |   536K|    77M| |  2624   (2)| 00:00:37 |
|   4 |    VIEW                      |                       |  2364K|    74M| | 16424   (2)| 00:03:50 |
|   5 |     SORT UNIQUE              |                       |  2364K|    49M|72M| 16424  (86)| 00:03:50|
|   6 |      UNION-ALL               |                       |       |       ||            |          |
|   7 |       INDEX FAST FULL SCAN   | ACCR_SIS_PURCH_DTL_PK |   375K|  8077K||   871   (1)| 00:00:13 |
|   8 |       TABLE ACCESS FULL      | ACCR_SIS_EXCL_DTL     |  1988K|    41M||  5634   (1)| 00:01:19 |
|   9 |   TABLE ACCESS BY INDEX ROWID| MT_CMPNY_VNDR         |     1 |    28 | |     1   (0)| 00:00:01 |
|* 10 |    INDEX UNIQUE SCAN         | MT_CMPNY_VNDR_PK      |     1 |       | |     0   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   2 - access("SRC2"."PGM_MSTR_NBR"="ACCR2"."PGM_MSTR_NBR" AND
              "SRC2"."PGM_TRK_NBR"="ACCR2"."PGM_TRK_NBR" AND "SRC2"."CNTL_LOCN"=
"ACCR2"."CNTL_LOCN")
  10 - access("LKP3"."CMPNY_VNDR_NBR"(+)="SRC2"."CMPNY_VNDR_NBR")
Statistics
        102  recursive calls
          0  db block gets
      34558  consistent gets
      23241  physical reads
         88  redo size
     531258  bytes sent via SQL*Net to client
       2760  bytes received via SQL*Net from client
        361  SQL*Net roundtrips to/from client
          1  sorts (memory)
          0  sorts (disk)
       5392  rows processed

Answer 1

With respect to HASH JOIN it has two operands a TABLE ACCESS FULL and VIEW. Oracle joins these results together based on the following access predicate:
2 - access("SRC2"."PGM_MSTR_NBR"="ACCR2"."PGM_MSTR_NBR" AND
              "SRC2"."PGM_TRK_NBR"="ACCR2"."PGM_TRK_NBR" AND "SRC2"."CNTL_LOCN"="ACCR2"."CNTL_LOCN")The VIEW is the result of the union between the CASADM.ACCR_SIS_PURCH_DTL and CASADM.ACCR_SIS_EXCL_DTL where instead of accessing the table CASADM.ACCR_SIS_PURCH_DTL Oracle was able to acquire all the data from the index ACCR_SIS_PURCH_DTL_PK .
The TABLE ACCESS FULL is exactly what says a full table access of SBA_REB_PGM.
The NESTED LOOPS OUTER has two operands like the HASH JOIN. The way this works is that for each result returned by the HASH JOIN operation it accesses the index MT_CMPNY_VNDR_PK and then the table MT_CMPNY_VNDR based on the following access predicate:
10 - access("LKP3"."CMPNY_VNDR_NBR"(+)="SRC2"."CMPNY_VNDR_NBR")It'd probably be worthwhile for you to review the following paper by Christian Antognini Interpreting Execution Plans as well.