Sometimes you need to change service accounts password for a farm after it was built and configured for various reasons:
1. security team hounds you and you have to periodically change service accounts passwords
2. your SharePoint admin guy leaves the company and you don't trust him/her
3.consultant comes in and configures your farm (refer to number 2 above)
4. you are of the Chicago's school of thought "Vote early and vote often" and extend it to service accounts password security......
There are couple of blog
posts out there that talk about how to change passwords for SharePoint 2010
manages service accounts. You can do it using the GUI (Central Admin) or
powershell.
I actually had to go through this exercise recently, and what I found is
that certain service applications will stop working after the passwords have
been updated. Specifically, the user profile synhronization service stops (big surprise), and
the search service application enters paused state.
After you change the passwords, you should probably check and make sure the
underlying services are running. The two Forefront Identity
Management services on which UPS depends will be stopped. Don't try to
start them manually, instead do it through Central Administration > Manage
Services on Servers. You will be prompted to re-enter the password for your farm
account.
Additionally, you may need to update the password for SharePoint
Server Search 14 service. In my case it was straightforward, I rebooted
my index server and the service was stopped complaining of logon failure. I just
updated the credentials in services.msc snap-in and started the service
manually.
There is one more step to get search working again, and that is to resume
the search service application from powershell.
Run get-spserviceapplication, this will give you list of
all service app IDs.
Copy the ID for your search service app and then run:
resume-spenterprisesearchserviceapplication -identity
.
This will resume the service app, and your scheduled crawls will start
running again.