https://www.ibm.com/docs/en/sanvolumecontroller/8.6.x?topic=htrlos-attachment-requirements-hosts-that-are-running-linux-operating-system

You must ensure the following configuration settings to restore the path if they are lost during an upgrade or other hardware maintenance that results in a node being offline:

• SCSI INQUIRY TIMEOUT
• SCSI COMMAND TIMEOUT
• Multipath settings in multipath.conf

For Redhat

To make the change permanent, edit /etc/sysconfig/grub and add to the GRUB_CMDLINE_LINUX line:

scsi_mod.inq_timeout=70

Run the following command to rewrite the boot record:

grub2-mkconfig -o /etc/grub2.cfg

Use the following command to change the inq_timeout parameter temporarily without rebooting:

echo 70 > /sys/module/scsi_mod/parameters/inq_timeout

In RHEL6, RHEL7, RHEL8, SLES12, and SLES15 enter the following command to view that the change was made:

systool -m scsi_mod -A inq_timeout

To set the SCSI COMMAND TIMEOUT

  Set the udev rules for SCSI command timeout to 120s. This is the recommended setting for all versions of Linux.

To increase the SCSI command timeout for the system, create the following udev rule:

# Set SCSI command timeout to 120s (default == 30 or 60) for IBM 2145 devices
SUBSYSTEM=="block", ACTION=="change", ENV{ID_VENDOR}=="IBM",ENV{ID_MODEL}=="2145", RUN+="/bin/sh -c 'echo 120 >/sys/block/%k/device/timeout'"

To reload the udev rules without rebooting (or dynamically) you can run the following commands:

udevadm control -R
/sbin/udevadm trigger --type=devices --action=add