2486887 - Error ORA-12154 while calling brconnect in the upgrade phase MAIN_SWITCH/XCNV_DUMP or in phase PREP_INSTALL/SHDINST_DB_PREP

The upgrade process is ended with error while calling brconnect in the upgrade phase MAIN_SWITCH/XCNV_DUMP in SUM. 

Error message with the following pattern is found in the log file XCNVDUMP.LOG.
**********************
 3 ETQ121 <time stamp>: PID <pid> execute '~/exe/brconnect -u -p ~/tmp/SPACESTAT.LST -c -f stats -f allsel,collect,space -p 6 -r 16 -RDB' in background, output written to '<SUM>/abap/log/ORA_SPACESTAT.LOG'.
 3WETQ122 <time stamp>: PID <pid> exited with status 3 (time: 165.0/ 0.0/ 0.0/171MB real/usr/sys/maxmem)
 4 ETQ399 <time stamp>: WAITED for 1 processes to finish, 0 aborted.
 1EETQ399 Last error code set is: brconnect exited with 3
 1EETQ204 Upgrade phase "XCNV_DUMP" aborted with severe errors ("<time stamp>")
**********************

The detailed information with the following pattern can be found in the log file ORA_SPACESTAT.log.
**********************
EXECUTING <SUM>/abap/exe/brconnect -u -p <SUM>/abap/tmp/SPACESTAT.LST -c -f stats -f allsel,collect,space -p 6 -r 16 -RDB
 BR0801I BRCONNECT <Version>
 BR0280I BRCONNECT time stamp: <time stamp>
 BR0262I Enter database user name[/password]:
 BR0805I Start of BRCONNECT processing: cevpqypa.sta <time stamp>
BR0484I BRCONNECT log file: <SUM>/abap/tmp/cevpqypa.sta
BR0278E Command output of 'sqlplus /nolog < /dev/null':
Error 6 initializing SQL*Plus                                                          
SP2-0667: Message file sp1<lang>.msb not found                       
SP2-0750: You may need to set ORACLE_HOME to your Oracle software directory
 BR0280I BRCONNECT time stamp: <time stamp>
 BR0279E Return code from 'sqlplus /nolog < /dev/null': 1
 BR0302E SQLPLUS call for database instance <SID> failed
 BR0303E Determination of Oracle version failed
 BR0280I BRCONNECT time stamp: <time stamp>
 BR0301E SQL error -12154 at location db_connect-2, SQL statement:
 'CONNECT SYSTEM/**********@XD0'
 ORA-12154: TNS:could not resolve the connect identifier specified
 BR0310E Connect to database instance <SID> failed
BR0806I End of BRCONNECT processing: cevpqypa.sta <time stamp>
 BR0280I BRCONNECT time stamp: <time stamp>
 BR0804I BRCONNECT terminated with errors
**********************

SAP ABAP System with Oracle Database

MAIN_SWITCH/XCNV_DUMP, brconnect, TNS_ADMIN, sp1<lang>.msb, ORA-12154, PREP_INSTALL/SHDINST_DB_PREP , KBA , BC-UPG-TLS-TLA , Upgrade tools for ABAP , BC-DB-ORA , Oracle , Problem