3299767 - DB6: R3trans hangs at function call "recvfrom"

SAP system gets hang. Following symptoms are noticed:

• Command "db2 connect to <SID>"  is working fine on database.
• "R3trans -d" gets hang.

The generated trans.log shows the last entry as: "Connected ...."

4 ETW000  [     dev trc,00000]  Running with CLI driver.
4 ETW000  [     dev trc,00000]  Fri Jan 27 09:58:58 2023
4 ETW000  [     dev trc,00000]  CLI cfg for con_hdl=0:
4 ETW000  [     dev trc,00000]  DSN="ABC";UID="SAPABC";DATABASE=ABC;PROTOCOL=TCPIP;HOSTNAME=12345ABC00p;SERVICENAME=5912;
4 ETW000  [     dev trc,00000]  Connected to DB server type 'DB2/LINUXX8664'
4 ETW000  [     dev trc,00000]  Connected to DB server version '11.05.0700'
4 ETW000  [     dev trc,00000]  CURRENT DEGREE is 'ANY' .
4 ETW000  [     dev trc,00000]  Connected to 'ABC' as 'SAPABC' schema 'SAPABC' o.k.
4 ETW000  [     dev trc,00000]  Connected: con_hdl=0 ; appl_hdl=88888; appl_id="10.222.22.23.27452.230127015858" 
4 ETW000  [     dev trc,00000]  Current member="10.222.22.22:5912" 
4 ETW000  [     dev trc,00000]  Database code page is ok.
4 ETW000  [     dev trc,00000]  Database collating sequence is ok.
4 ETW000  [     dev trc,00000]  DB2_WORKLOAD=SAP is set in DB2 registry as required.
4 ETW000  [     dev trc,00000]  CLI Insert Buffering is disabled on single partition databases.
4 ETW000  [     dev trc,00000]  INFO: Unable to determine SAPDBHOST; defaulting to 'UNKNOWN'
4 ETW000  [     dev trc,00000]  Connection 0 opened (DBSL handle 0)
4 ETW000  [     dev trc,00000]  INFO: Unable to determine SAPDBHOST; defaulting to 'UNKNOWN'
4 ETW000  [     dev trc,00000]  NTAB: version is VERS_B, UNICODELG=2, SAP_UC_LN=2
4 ETW000 Connected to DBMS = DB6 --- DB2DBDFT = 'ABC' --- SYSTEM = 'ABC'.   <<<<< Last entry

OS trace collected following note 1730855 shows it is stuck at function call "recvfrom"

09:58:14.235484 sendto(4, "\0\203\320Q\0\1\0} \f\0D!\23P06               "..., 195, 0, NULL, 0) = 195
09:58:14.235531 recvfrom(4, "\0002\320R\0\1\0,\"\5\0\6\21I\0\0\0\6!\2$\27\0\5!P\1\0\f![\0"..., 131072, 0, NULL, NULL) = 407
09:58:14.235831 write(3, "4 ETW000 Connected to DBMS = DB6"..., 74) = 74   <<<<< This matches the last entry of R3trans
09:58:14.235946 uname({sysname="Linux", nodename="xc-s-zl18186", ...}) = 0
09:58:14.236001 sendto(4, "\0\203\320Q\0\1\0} \f\0D!\23P06               "..., 183, 0, NULL, 0) = 183
09:58:14.236053 recvfrom(4, "\0002\320R\0\1\0,\"\5\0\6\21I\0\0\0\6!\2$\27\0\5!P\1\0\f![\0"..., 131072, 0, NULL, NULL) = 391
09:58:14.236306 sendto(4, "\0\203\320Q\0\1\0} \f\0D!\23P06               "..., 183, 0, NULL, 0) = 183
09:58:14.236353 recvfrom(4, "\0002\320R\0\1\0,\"\5\0\6\21I\0\0\0\6!\2$\27\0\5!P\1\0\f![\0"..., 131072, 0, NULL, NULL) = 90
09:58:14.236547 sendto(4, "\0l\320\1\0\1\0f \6\0D!\23P06               "..., 108, 0, NULL, 0) = 108
09:58:14.236592 recvfrom(4, "\4\274\320S\0\1\4\266$\33\377\0\0\tPATCHHIST\1\0\1\27L\0\1\0\0"..., 131072, 0, NULL, NULL) = 1339
09:58:14.236866 sendto(4, "\0N\320Q\0\1\0H \r\0D!\23P06               "..., 308, 0, NULL, 0) = 308
09:58:14.236914 recvfrom(4, "\0Y\320C\0\1\0S$\10\0\0\0\0\00000000SQL11057\0\0\0\0"..., 131072, 0, NULL, NULL) = 319
09:58:14.237136 sendto(4, "\0S\320Q\0\1\0M \v\0D!\23P06               "..., 357, 0, NULL, 0) = 357
09:58:14.237181 recvfrom(4, 0x7f838eadc080, 131072, 0, 0, 0) = ? ERESTARTSYS (To be restarted if SA_RESTART is set)  <<< It hangs here
09:45:42.897044 --- SIGWINCH {si_signo=SIGWINCH, si_code=SI_KERNEL} ---   
09:45:42.897105 recvfrom(4, 0x7f838eadc080, 131072, 0, 0, 0) = ? ERESTARTSYS (To be restarted if SA_RESTART is set)

• SAP on IBM Db2 for Linux, UNIX, and Windows
• Application server and database server are on Cloud

R3trans, recvfrom, ERESTARTSYS , KBA , BC-DB-DB6 , DB2 Universal Database for Unix / NT , Problem