8.4. Using RHN DB Control

RHN Satellite with Embedded Database requires a utility for managing that database. Red Hat provides just such a tool: RHN DB Control. This command line utility allows you to do everything from make, verify, and restore backups to obtain database status and restart it when necessary. You must be the oracle user to invoke RHN DB Control. To begin, switch to the oracle user:
su - oracle
Next, issue the following command:
db-control option

8.4.1. DB Control Options

RHN DB Control offers many command line options. To use them, as oracle insert the option and the appropriate value, if needed, after the db-control command.

Table 8.1. RHN DB Control Options

Option Description
help Lists these db-control options with additional details.
backup DIRNAME Backs up the database to the directory specified.
examine DIRNAME Examines the contents of a backup directory. Returns the timestamp of backup creation and reports on its contents.
extend Increase the RHN Oracle tablespace
gather-stats PCT Gather statistics on RHN Oracle database objects. PCT is the percentage of rows to estimate (the default is 15%).
report Reports on current usage of database space.
report-stats Reports on segments with stale or empty statistics.
restore DIRNAME Restores the database from backup kept in DIRNAME. Database must be stopped for this command to run successfully.
start Starts the database instance. This can also be accomplished by issuing the service oracle start command as root.
shrink-segments Shrinks RHN Oracle database segments with signifcant amounts of free space.
status Shows the current status of the database, either "running" or "offline".
stop Stops the database instance. This can also be accomplished by issuing the service oracle stop command as root.
tablesizes Show space report for each table
verify DIRNAME Verifies the contents of the backup kept in DIRNAME. This command runs a checksum of each of the files kept in the backup.

Note

Database statistics are collections of data that describe more details about the database and the objects in the database. These statistics are used by the query optimizer to choose the best execution plan for each SQL statement. Because the objects in a database can be constantly changing, statistics must be regularly updated so that they accurately describe these database objects. Statistics are maintained automatically by Oracle. However, if your database has performance issues after a significant amount of data changes, consider performing manual gathering of statistics.

Note

After deleting large amount of data, use the segment-shrink feature to reclaim fragmented free space in an Oracle Database segment. The benefits of segment-shrink are compaction of data that leads to better cache utilization and the compacted data requires fewer blocks to be scanned in full table scans, which both lead to better performance.
The segment shrink feature works only on newly created Oracle Database 10g Release 2 that comes with RHN Satellite Server 5.2.0. Due to different default database settings in Oracle Database 9i this feature does not work on databases that were upgraded from previous RHN Satellite Server releases.