Backing Up the Database

This chapter describes the Cisco Access Registrar shadow backup facility, which ensures a consistent snapshot of Cisco AR's database for backup purposes.

Because the Cisco AR's database (called MCD) does a variety of memory caching, and might be active at any time, you cannot simply rely on doing system backups to protect the data in the database. At the time you run a system backup, there could be Cisco AR operations in progress that cause the data copied to the system backup tape to be inconsistent and unusable as a replacement database.

To ensure a consistent backup, Cisco AR uses a shadow backup facility. Once a day, at a configurable time, Cisco AR suspends all activity to the database and takes a snapshot of the critical files. This snapshot is guaranteed to be a consistent view of the database, and it is preserved correctly on a system backup tape.

Configuration

The only configuration for this facility is through a single entry in the system Registry at $INSTALL/conf/car.conf is the registry path to this item.

This entry is a string that represents the time-of-day at which the shadow backup is scheduled to occur (in 24 hour HH:MM format). The default is 23:45.

When you remove this entry or set it to an illegal value (for example, anything that does not begin with a digit), backups are suppressed. The server is otherwise unaffected.

Command Line Utility

In addition to being available at a scheduled time of day, you can also force a shadow backup by using the mcdshadow utility located in the $INSTALL/bin directory. There are no command-line arguments.

This might take a few minutes to complete as a full copy of the database is created.

Recovery

When it is necessary to use the shadow backup to recover data, either because the regular working database has been corrupted by a system crash, or because the disk on which it resides has become corrupted, perform the following:

Step 1 Stop all Cisco AR servers.

Step 2 Make sure three files (mcddb.d01, mcddb.d02, and mcddb.d03) exist in the $INSTALL/data/db.bak directory.

Step 3 Copy the files into the $INSTALL/data/db directory. Do not move them because they might be needed again.

Step 4 Change directory to the $INSTALL/data/db directory.

cd  $INSTALL/data/db

Step 5 Rebuild the key files by typing the command:

$INSTALL/bin/keybuild mcddb

This might take several minutes.

Step 6 As a safety check, run $INSTALL/bin/dbcheck mcddb (UNIX) to verify the integrity of the database. Note, you must be user root to run dbcheck.

No errors should be detected.

mcdshadow Command Files

The mcdshadow command uses the files listed in Table 21-1.

Table 21-1 mcdshadow Files 

File
Description

mcddb.dbd

Template file that describes the low-level data schema for the Raima run-time library.

mcddb.k01
mcddb.k02
mcddb.k03

Key files that contain the data that is redundant with the data files. Cisco AR does not back up these files because they can be completely rebuilt with the keybuild command.

mcdcd.d01
mcdcd.d02
mcdcd.d03

Data files that contain the backup.

mcdConfig.txt

Text file from which Cisco AR configures the initial at-install-time database.

mcdschema.txt

Text file that contains a version number denoting the level of the schema contained in the dbd file. Cisco AR will not attempt to open the database unless the number in this file matches a constant that is hard-coded in the libraries. If the result of the mcdshadow command (which uses copies of the data files) is divorced from its original mcdschema.txt, you will not be able to run Cisco AR.

vista.taf
vista.tcf
vista.tjf

Working files used by the Raima run-time library to ensure transactional integrity.