Explanation:
The RESYNC CATALOG command performs a full resynchronization of the recovery catalog. Resynchronizations can be full or partial. When full, RMAN updates all changed records for the physical schema: data files, table spaces, redo threads, and online redo logs. If the database is open, RMAN also obtains data about rollback segments. When partial, RMAN reads the current control file to update data, but does not resynchronize metadata about the physical schema or rollback segments. Incorrect Answer:
1: The LIST command is used to display information about backup sets, proxy copies, and image copies recorded in the repository. The LIST command displays the files against which you can run CROSSCHECK and DELETE commands.
2: The SWITCH command specifies that a data file copy is now the current data file, that is, the data file pointed to by the control file.
3: Use this command to examine a backup set and report whether it can be restored. RMAN scans all of the backup pieces in the specified backup sets and looks at the checksums to verify that the contents are intact so that the backup can be successfully restored if necessary.
4: Purpose of this command to configure persistent settings affecting RMAN backup, restore, duplication, and maintenance jobs. These configurations are in effect for any RMAN session until the configuration is cleared or changed.
6: You need to use this command to upgrade the recovery catalog schema from an older version to the version required by the RMAN executable. For example, if you use a release 8.0 recovery catalog with a release 8.1 version of RMAN, then you must upgrade the catalog.
Reference:
OCP Oracle 9i Database: Fundamentals II Exam Guide, Rama Velpuri, p. 397-398
Chapter 17: Recovery Catalog Creation and Maintenance

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