You're welcome. Sorry but I neither represent NetApp nor I represent NetApp support, and more so it is not advisable to take 'forum threads' as authority or any sort of guarantee. It's just a place to help each other with queries & troubleshooting of NetApp products. You are more than welcome to open a support case to get more clarification around this.
Coming to your query regarding the confirmation, I just want to say that, LUN is a BLOCK device and once it is mapped to HOST, it is up to HOST to layer/partition it and manage it. NetApp owns only the 'LUN' (BLOCK FILE) and it provides WAFL snapshot to ensure the data integrity within the FILER is guaranteed and can be restored back to its previous point-in-time snapshot. Even more cool is the feature called 'flexclone', I am sure you have used this before. This will allow you to not only test-resizing but give you all the confidence to perform same steps on the production file-system.
However, that does not mean that NetApp does not provide any help in regards to OS interoperability with NetApp ONTAP. Each supported OS is well tested with features and it further provides Best Practices (Recommended settings to be used with Host OS & ONTAP) and Host side Utilities that you can download for free and manage the LUN more efficiently.
Solaris Host Utilities with NetApp ONTAP:
https://docs.netapp.com/us-en/ontap-sanhost/hu_solaris_114.html#installing-the-solaris-host-utilities
Assuming that the Solaris is using some kind of volume manager on the host side (I am saying this purely based on my experience with redhat/centos LVM, talk to your Solaris team).
High-level steps will be:
1) Resize Vol/LUN in FILER
2) Get the host OS to see the new LUN size
3) Get the 'whatever volume manager' you are using to increase the available space in diskgroup/pv
4) Get the new diskgroup/pv to increase the size of the volume
5) Grow the filesystem on the volume to use the increased space.
On the side note: I have worked with Oracle DB/Unix team in the past, and every time there was an update to be patched on the 'Production server', application services were stopped, file-system was cleanly unmounted, and ONTAP snapshot was taken. At times, update were successful, and at times update failed, and when it failed, we were asked to 'revert' to last point-in-time snapshot, and it worked all the time. Therefore, as as long as you have taken a snapshot of the Volume (hosting the LUN) prior to re-sizing the LUN, you can always revert it back in case anything goes wrong.
If you want to be 100% sure if it will work, follow these steps:
1) Ensure flexclone is licensed.
2) volume clone the production vol/lun that is hosting the Solaris LUN
3) Map the cloned_solaris_LUN to a Solaris test box and mount it.
4) check if the file-system is read/writable and existing-data can be read/write fine.
5) unmount the file-system
6) resized the cloned_volume
7) resized the cloned_lun
😎 Do the steps mentioned in the high-level steps from the host side to grow the space.
9) If it works, that means you can go ahead with the plans on the Production server