1. What are the tasks of a MaxDB database administrator?
The MaxDB administrator is responsible for monitoring the active database and also for the following activities:
- Backing up the dataset and the log area
- Executing consistency checks on the dataset to eliminate inconsistencies in the database that are caused by hardware defects.
- Updating the optimizer statistics (Update Statistics).
- Executing performance analyses.
- Monitoring the free memory.
2. What administration tools are available?
SAP recommends that you use the MaxDB tools DBMGUI/Database Studio, DBMCLI and SAP CCMS for the administration tasks.
3. Can administration tasks be automated?
You can use the CCMS scheduling calendar or the MaxDB tools to automate both administration tasks that need to run regularly (such as automatic log backups, Update Statistics) or that only need to be run when required (such as extending the data area).
More information about this topic is available is in the MaxDB documentation (Note 767598) in the glossary, under the keyword "Automation".
4. Is there a central transaction in the SAP system for all administrative database activities?
In the MaxDB environment, you can use the transaction DB50: Database Assistant to monitor the database.
You can use transaction LC10: liveCache Assistant to monitor a liveCache. In SAP Releases as of Release 7.0, you access these transactions using transaction DB59.
As of SAP Release 7.0 the DBA Cockpit (transaction dbacockpit) is available as a central access to the database or liveCache administration.
5. Where can I find more information about MaxDB CCMS?
Information about MaxDB/liveCache CCMS is available in the MaxDB documentation and in Note 990602: FAQ: CCMS for MaxDB and liveCache
6. What is the central scheduling calendar?
The central CCMS scheduling calendar comprises transactions DB13 and DB13C. You can use these transactions to schedule the following activities:
- Back up the dataset area and the log area
- Check backups for completeness
- Update the optimizer statistics
- Database structure checks
7. Can I administrate several systems using a single central scheduling calendar?
Yes. You can use transaction DB13C to administrate external databases from a central SAP system. Transaction DB13C is available as of SAP Basis Release 6.10.
8. How do I perform a database backup?
To perform a database backup, use the MaxDB backup tools DBMGUI or DBMCLI. You can use the scheduling calendar (DB13 or DB13C) to schedule a backup for a particular point in time and execute it implicitly.
It is possible to execute file system backups of MaxDB volumes when the database is offline only, though we recommend this only in exceptional circumstances (such as if you use snapshots or split-mirrors).
9. Are logs also saved during a database backup?
No. A database backup using the MaxDB tools only backups up the data that is stored in the data volumes. This includes the actual use data and the "before images", so that it is possible to restore a consistent database using only the database backup.
The data that is saved in the log volume is not backed up during a data backup.
Further information about MaxDB logging is available in Note 869267 FAQ: MaxDB LOG area.
10. What advantage does a backup using the MaxDB backup tool offer compared to a file system backup?
It is only possible to execute a file system backup when the database is in the offline status. The length of time for which the database is unavailable for operation depends on the size of the dataset.
In contrast, you can back up the database while it is in the online status using the MaxDB backup tools, in parallel with production operation. You can use a backup generated online using database tools for a system copy.
A file system backup of the volumes (data and log) backs up all data that is saved in the volume.
In contrast, a backup using the MaxDB tools only backs up the data of a converter version, which may be required for a recovery.
When you create a file system backup, the system does not carry out a checksum-check on the blocks.
While the backup is being created using the MaxDB tools, the system executes consistency checks on the data.
Even when you back up the log volumes using a file system backup, you need to also back up the log area using the database tools, to ensure that the log area can be released again for overwriting.
A file system backup is not included in the MaxDB backup history.
Backups performed using the MaxDB tools integrate the backup history, and this makes restoring the database in the event of a recovery a simple process.
11. Does MaxDB support the use of external backup tools?
Yes. Max DB supports a number of backup tools from third parties, such as Networker, Netbackup from Veritas, and so on.
Which specific tools are supported, and how they can be included in a MaxDB environment is described in the MaxDB documentation (Note 767598). Search the glossary for the keyword "external backup tool".
Scripts in the database manager also enable you to use all other backup tools that are able to process backups from pipes.
12. Does MaxDB support split-mirror technology and snapshots?
Yes. Refer to Note 371247 SAP DB and "Split Mirror" techniques.
13. Where can I find information about MaxDB High Availability?
Refer to Note 952783: FAQ: MaxDB high availability
14. How do I perform a log backup?
For more information on this topic, refer to the MaxDB documentation and Note 869267.
15. Where can I find more information about MaxDB logging?
In addition to the MaxDB documentation (note 767598, keyword "log*"), also refer to Note 869267.
16. What is a Check Data or VERIFY?
During a database structure check (Check Data or VERIFY), the database system checks whether the database structures are consistent (for example the consistency of the B* trees), but not the semantics of the data model. Therefore you cannot use a database structure check to find any logical errors.
17. Where can I find more information about database structure checks?
For more information about database structure checks (Check Data/VERIFY), refer to the FAQ Note 940420.
18. What is an Update Statistics?
The SQL optimizer requires the statistics in order to determine the optimum search strategy for data access when processing complex SQL statements that have specific search conditions.
19. Where can I find more information about Update Statistics?
For more information, see Note 927882 (FAQ: MaxDB Update Statistics).
20. How can I monitor the fill factor of my database?
Use transaction DB50 -> Current Status -> Memory Areas -> Data Area to determine the fill factor of your database.
The system table 'serverdbstatistics' displays information about the fill factor of a database.
As of MaxDB Version 7.6, the system table 'serverdbstatistics' contains the pages that contain log information (UNDO and history pages), as well as the actual use data.
History pages are no longer required, once the transaction is committed. After a savepoint, the garbage collector can then remove the history pages, and the memory is released again.
The SQL statement on the system table 'files' only determines the amount of memory that data pages consume in the database.
SUM (treeleavessize) "Leaf", SUM (lobsize)"Long-Long"
This calculation ignores pages that are within the data area, but which are occuppied by HISTORY and UNDO data.
The history information is contained in the system table 'historyinfo'.
SELECT SUM (pagecount) FROM historyinfo
21. How can I log the growth of individual tables?
Refer to Note 352081 Additional service-relevant functions for SAP DB.
22. What do I do if the data area is full?
When there is no more memory available in the database, the database hangs. You must make free memory available in the form of a new data volume. You can add new volumes while the database is online.
More information about this topic is available is in the MaxDB documentation (Note 767598) in the glossary, under the keyword "data volume" or "db_addvolume".
23. What do I do if the log area is full?
See Note 869267.
24. How can I determine if there is still activity on the database?
You can use the task manager or database console (x_cons) in transaction DB50/LC10 to determine if activities are still taking place on the database.
More information about this topic is available is in the MaxDB documentation (Note 767598) in the glossary, under the keyword "console".
25. What do I do if there are no free database sessions left, and no new database application can log on to the database?
The general parameter MAXUSERTASKS defines the maximum number of user tasks that can be active at the same time, and therefore determines the maximum number of database sessions.
When this number is reached, no further users can log on to this database instance. You then need to increase the parameter. If you assign a very high value to MAXUSERTASKS, then the database system requires a lot of address room, especially in the case of local communication using shared memory.
The change only becomes active when you restart the database.
26. How can the database become smaller after an Export/Import using R3load?
A database that has continually grown due to INSERTs, UPDATEs and DELETEs contains leaf pages in the B* trees that are not 100% full. For example, if the data record does not fit in the corresponding page during an INSERT, the system creates a new page. The system writes the new data record and half the data records of the page that was too small for the INSERT to this new page. The corresponding records of the original page are deleted.
When you use R3load (IMPORT) to structure the database, the INSERTS follow the primary key sequence. The system also adds the data records to the B* tree in this sequence, and so the data pages can be more thoroughly utilized.
You can use the following SQL statement to check the utilization of the data pages (caution: this statement analyzes and locks the entire B* tree of the corresponding table):
SELECT * FROM tablestatistics WHERE tablename = '<tablename>'
27. Where do I find more information about MaxDB Administration?
More information about this topic is available is in the MaxDB documentation (Note 767598) in the glossary, under the keyword "administration".
Alternatively, you can use the SDN to access the MaxDB documentation.