3318611 - SUM: RFC failed with code 5 key DBCON_INSERT

Upgrade fails due to known issue with outdated version of SUM.
You need to reset SUM and use the latest version.

After reset, upgrade fails with following error in phase 'MAIN_SHDINST/CREATEDBCON_SHD', which is responsible for creating the database connection for the shadow instance of the SAP system.

SAPup.log

CURRENTPHASE MAIN_SHDINST/CREATEDBCON_SHD
...started at 20230312230335
# Using phase log file 'CREATEDBCONSHD.LOG'.
...finished at 20230312230336 with status FAILED.
# Error message set: 'RFC system N58 nr 00 function 'CREATE_SHDDBCON'
RFC failed with code 5 key DBCON_INSERT:
 Number:000'
...begin dialog at 20230312230338

CREATEDBCONSHD.LOG

1 ETQ206 Executing pre-phase DB specific actions 0/1.
1 ETQ200 Executing actual phase 'MAIN_SHDINST/CREATEDBCON_SHD'.

<snipped>

1EETQ235 Call of function module "CREATE_SHDDBCON" by RFC failed (error-status "5")
2EETQ360 RFC of "CREATE_SHDDBCON" failed:
2EETQ361 code/exception  : 5
2EETQ362 key             : DBCON_INSERT
2EETQ399  Number:000

• SAP NetWeaver ABAP system

CREATEDBCON_SHD, CREATE_SHDDBCON, DBCON_INSERT, RFC failed, code 5 , KBA , BC-UPG-TLS-TLA , Upgrade tools for ABAP , How To