TPG enable after disabling it on iscsi target does not allow initiator to perform read/writes on the iscsi disks

[linonymous]

Following is the scenario.

• Steps:

1. Created a target, added LUNs, ACLs, and portals (CHAP authentication is disabled)
2. Discovered these LUNs from iSCSI Initiator, created a filesystem on the iSCSI disks, and performed read/writes
3. Disabled the TPG of the target and again enabled it on the iSCSI target machine.
4. On iSCSI initiator side, now I am not able to perform read/writes, it gives "I/O error"

• The configuration of the machines:

1. iSCSI Target machine:
   [root@linonymous1 /]# cat /etc/redhat-release
   Red Hat Enterprise Linux Server release 7.3 (Maipo)
   [root@linonymous1 /]# rpm -qa targetcli
   targetcli-2.1.fb46-1.el7.noarch
   [root@linonymous1 /]# rpm -qa | grep rtsl
   python-rtslib-2.1.fb63-2.el7.noarch

2. iSCSI Initiator machine:
   [root@sprip4_01 ~]# cat /etc/redhat-release
   Red Hat Enterprise Linux Server release 7.4 (Maipo)
   [root@sprip4_01 ~]#rpm -qa | grep iscsi
   iscsi-initiator-utils-iscsiuio-6.2.0.874-7.el7.x86_64
   iscsi-initiator-utils-6.2.0.874-7.el7.x86_64

• The workaround
  Restart the target daemon on the target side.

Could you please tell why is it that case? and why does it happen?

[linonymous]

While disabling the TPG I am removing the disk where LUNs are stored, and reattach it when it comes online. @pkalever @agrover does this affects the targetcli configuration? what is the flow?