Managing Copies of the Database

AP maintains a database that contains information about all defined metadisks and metanetworks, and their corresponding alternate paths and properties. One set of data is maintained for each domain on the Sun Enterprise 10000 server. On other Sun Enterprise servers, one set of data is maintained for the entire machine. However, you should set up multiple copies of the database. In this way, if a given database copy is not accessible or becomes corrupted, AP can automatically begin to use a current, non-corrupted database copy.

You must dedicate an entire disk partition, one that has at least 300 Kbytes, to each database copy. You can use larger partitions, but doing so wastes disk space. Keep the following information in mind when selecting disk partitions for the AP database:

• You should set up three to five database copies.

• As configured at the factory, partition four of the root disk is appropriately sized for the AP database and is not allocated for any other purposes. This partition is a good choice for an AP database copy, assuming you are not using it for other purposes.

• The database copies should have no I/O controllers in common with each other. Following this rule allows maximum availability in case of controller failure.

• If you have configured your system to make use of Dynamic Reconfiguration (DR), the database copies should be hosted by I/O controllers on different system boards so that a database copy is accessible if one of the system boards is detached.

• If you want to place an AP database copy in a partition of an alternately pathed disk, create two copies of the database using each of the physical paths utilized by the AP metadisk to access the partition. AP behaves as if two copies of the database exist, when actually, there is only one, since the disk is accessible via two paths. The behavior does not result in database inconsistencies, however, since AP always updates and accesses database copies sequentially. This behavior does not result in performance problems since the AP database is not accessed frequently.

On the Sun Enterprise 10000 server, a subset of the information in the AP database is automatically maintained on the SSP for use at boot time. This database contains AP information for the boot disk.

The following AP command examples assume that your command search path includes the directory where the commands are installed. See "Using Single-User Mode".

To Create a Copy of the AP Database

1. Use apdb(1M) as follows:

   # apdb -c /dev/rdsk/c0t1d0s4 -f

   The -c option specifies the raw disk slice (under /dev/rdsk) where you want to create the database copy. You must dedicate an entire disk partition to each database copy. The disk partition must have at least 300 Kbytes.

   The -f (force) option is only necessary to create the first AP database copy.

   ---

   Caution -

   Do not create an AP database using a metadisk path (rather than a physical path to the disk slice). If you use a metadisk path, the apdb(1M) command will succeed, but you may experience unpredictable behavior at a later point in time. If you want to place an AP database in a partition of an alternately pathed disk, create two copies of the database using each of the physical paths utilized by the AP metadisk to access the partition.

   ---

To Delete a Copy of the AP Database

1. Use apdb(1M) as follows:

   # apdb -d /dev/rdsk/c0t1d0s4 -f # apconfig -D #

   The -d option specifies the raw disk slice (under /dev/rdsk) where the copy of the database that you want to delete is located.

   The -f (force) option is only necessary to delete the second-to-last copy and the last copy of the database.

   In this example, apconfig -D is used after the deletion operation to view information about the existing AP database copies. Since no information is returned, the apdb(1M) command must have deleted the last database copy.