One of our customer is currently operating on IBM ACE 12.0.8.0 in UAT environment and IBM ACE 11.0.0.11 in production environment in AIX 7.2 TL5 operating system. 
They intend to upgrade to the latest mod release IBM ACE 12.0.10.0. They have observed recent modifications in the prerequisites, particularly around the XLC and gcc libraries for AIX. 

This is AIX library requirement for ACE 12.0.10.0

- XLC 17.1.1.4 runtime (see : https://www-01.ibm.com/support/docview.wss?uid=swg27038948 )
- gcc runtime at v8 or above

This is AIX library requirement for ACE 12.0.8.0

- XLC 16.1.0.3 runtime (see : https://www-01.ibm.com/support/docview.wss?uid=swg27038948 )
- gcc runtime at v6 or above

The customer has expressed some concerns regarding these updates with respect to rollback of the XLC and gcc library.

In the event of unforeseen issues or incompatibilities arising from the XLC update, they would like to rollback the XLC packages and gcc to a previous version. 

What are the steps involved in rolling back gcc 8 to gcc 6? 

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Sandeep Pal
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Hi,

It is not normal to downgrade / roll back your software packages particularly with many pre-requisites.

Particularly, difficult if you UAT has many users or concurrent use.

So the safe answer is take a backup then you can backout the downgrade.

Alternatively, clone the AIX disks and create a new virtual machine then you have the before and after available.

1. This could be a  disk clone using the disk subsystem.
2. mksysb and install it in the new VM.

Or you could snapshot your AIX disks, if using a shared storage pool (on the VIOS(s)).

One of our customer is currently operating on IBM ACE 12.0.8.0 in UAT environment and IBM ACE 11.0.0.11 in production environment in AIX 7.2 TL5 operating system. 
They intend to upgrade to the latest mod release IBM ACE 12.0.10.0. They have observed recent modifications in the prerequisites, particularly around the XLC and gcc libraries for AIX. 

This is AIX library requirement for ACE 12.0.10.0

- XLC 17.1.1.4 runtime (see : https://www-01.ibm.com/support/docview.wss?uid=swg27038948 )
- gcc runtime at v8 or above

This is AIX library requirement for ACE 12.0.8.0

- XLC 16.1.0.3 runtime (see : https://www-01.ibm.com/support/docview.wss?uid=swg27038948 )
- gcc runtime at v6 or above

The customer has expressed some concerns regarding these updates with respect to rollback of the XLC and gcc library.

In the event of unforeseen issues or incompatibilities arising from the XLC update, they would like to rollback the XLC packages and gcc to a previous version. 

What are the steps involved in rolling back gcc 8 to gcc 6? 

------------------------------
Sandeep Pal
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