downgrade problem 11.2.0.2 to 11.2.0.1 (ora-600 [qcisSetPlsqlCtx:tzi init]) problem solved

In case you encounter the following error, when downgrading from 11.2.0.2 to 11.2.0.1:

ORA-00600: internal error code, arguments: [qcisSetPlsqlCtx:tzi init]

There is a bug, but the documentation isn't much help unless you are familiar with how Oracle uses timezone files.

The error is caused by the fact that the upgrade will have upgraded your timezone version from "11" to "14".

(to find out what version you have:  select value$ from sys.prop$ where name = 'DST_PRIMARY_TT_VERSION';)

Not a problem unless you are downgrading.

But if you are downgrading, the version "14" files will not be in your old 11.2.0.1 ORACLE_HOME.

The solution is to copy the files from the new 11.2.0.2 ORACLE_HOME into the old 11.2.0.1 ORACLE_HOME: