1. Backup & Recovery 1

2. Agenda Backup Types Backup Process Model Backup Performance Tunning
Restore Types
Restore Process Model
Restore Performance Tunning
RollForward Performance Tunning 2

3. Backup Backup Types Online or Offline
Database Level backup or Tablespace Level backup
Full, Incremental or Delta 3

4. Offline Backup Database needs to be offline
Internally establishes connection to the specified database
Faster than online
Default option 4

5. Online Backup Database is accessible Needs archival logging enabled
Slower than offline backup
Log files are included by default
Incremental and delta 5

6. Incremental Backup
Copy of all data that has been updated since the last full successful backup
Cumulative backup
Need to maintain only the last incremental backup and last full backup
Database parameter TRACKMOD should be enabled
Incremental backup is not permitted until a full backup is taken to set a base from which it can recover 6

7. Incremental Delta Backup
Copy of all data that has been updated since the last any successful backup (full, incremental or delta)
Non cumulative
Need to maintain all backup images since the last full backup 7

8. Incremental Backup Granularity of tracking is at Tablespace level
Entire Large Objects are backed up if any other object in that Tablespace is modified
Normal data is backed up only if it has changed
In addition to the changed data incremental backup also includes the database's metadata
Not enabled by default due to minimal performance impact while tracking changes 8

9. Backup Process Model db2bm Buffer Manipulator
Reads data from the disk and writes into shared memory buffer
db2med
Media Controller
Reads from shared memory buffer and writes the pages out to the target devices
db2agent
Controls the flow between db2bm and db2med 9

10. Backup Process Model db2bm Controlled by PARALLELISM option
Reads data from disk into backup buffer
Sends full buffer message on the full queue for db2med 10

11. Backup Process Model db2bm
Function stack trace while waiting for the next available buffer
sqluReadAdrFromQueue
sqlubGetNextBuffer
Function stack trace while reading
pread64
sqloReadBlocks
Function stack trace after completing reading data
sqluReadMessageFromQueue
sqlubbuf 11

12. Backup Process Model db2med
Controlled by number of output destinations or Open Sessions clause when using TSM
Reads data from full buffers and writes to the media
Sends empty buffer message on the empty queue for db2bm 12

13. Backup Process Model db2med
Function stack trace while waiting for full buffer notification
sqluReadAdrFromQueue
sqluMCContinueBackup
Function stack trace while writing
write
sqlowrite 13

14. Backup Process Model db2agent
Responsible for setting up the message queues and spawn db2med and db2bm
Once backup starts db2agent process will wait for the backup complete notification
Function stack while waiting for notification
sqluReadMessageFromQueue
SqluxReadAgentQueue
sqlubcka 14

15. Backup Process Model Message queues.
Communication between db2agent, db2bm and db2med is managed by message queues
Following message queues created
1 message queue for the db2agent
1 message queue for full buffers
1 message queue for empty buffers
1 message queue for each db2bm edu
1 message queue for each db2med edu 15

16. Backup Process Model db2med with TSM db2vend process used
db2med invokes the TSM code inside db2vend 16

17. Backup Process Model db2vend
Independent process to execute the vendor API code
Similar to db2fmp
Runs outside DB2 address space
Prevents unexpected API errors from crashing DB2 17

18. Backup Performance Tuning
Backup command options
WITH num-buffers BUFFERS
PARALLELISM n
BUFFER buffer-size 18

19. Backup Performance Tuning
Backup command options
WITH num-buffers BUFFERS
Use at least twice as many buffers as backup sessions
which will not cause the target devices to wait for data
PARALLELISM n
Number of processes that are started to read data from the
database
Set n equal to the number of tablespaces being backed up
BUFFER buffer-size
Buffer-size is a multiple of the table space extent size plus one page 19

20. Backup Performance Tuning
If no options specified optimal values for number of buffers
buffer size and parallelism are selected automatically
db2diag.log entry shows the values that are selected
FUNCTION: DB2 UDB, database utilities, sqluxGetDegreeParallelism, probe:537
DATA #1 : <preformatted>
Autonomic BAR - using parallelism = 10.
FUNCTION: DB2 UDB, database utilities, sqlubTuneBuffers, probe:898
Autonomic backup - tuning enabled.
Using buffer size = 4481, number = 10. 20

21. Backup Performance Tuning
UTIL_HEAP_SZ
Uitlity Heap Size
Maximum memory that can be used simultaenously by Backup, Restore and LOAD
Used for backup buffers
More than buffer-size * number of buffers 21

22. Backup Performance Tuning
Fragmentation
db2bm reads contiguous blocks of data
Fragmentation due free extents can affect performance
REORG should be done to reduce fragmentation 22

23. Backup Performance Tuning
Prefetching
I/O performed by db2bm if tablespace has only one container
I/O performed by Prefetchers (db2pfchr) for tablespace with multiple containers
Parallel I/O improves performance 23

24. Backup Performance Tuning
Contention during online backup
db2bm must guarantee that the block of data being backed up does not change during the read operation
db2bm will wait on other shared users to complete their I/O operations to get exclusive access
db2n 24

25. Backup Process Model 25

26. Restore Restore Types Full database restore Tablespace restore
Redirect restore
Incremental Restore 26

27. Redirect Restore Used to restore database on a different machine
Restores tablespaces to a different location
Add, Change or remove containers of a DMS tablespace
Modify containers of a SMS tablespace 27

28. Redirect Restore Issue RESTORE command with REDIRECT option
db2 restore db sample redirect
Use SET TABLESPACE CONTAINERS command for each tablespace to specify the new container location
db2 set tablespace containers for 2 using (path '<path>')
Issue RESTORE command with CONTINUE option
db2 restore db sample continue 28

29. Redirect Restore Automatic Storage
Use ON option to set the path for automatic storage tablespaces
db2 restore db sample on <path> redirect
If no normal tablespaces then CONTINUE command
db2 restore db sample continue 29

30. Incremental Restore
Identify and restore the last incremental backup image
This restore only restores the metadata and not the actual data
Identify and restore the most recent full backup image
Restore the last incremental backup image again
This time the actual data will be restored 30

31. Incremental Restore
Use db2ckrst utility to get the correct restore sequence
db2ckrst -d <dbname> -t <timestamp>
Timestamp should be that of the last incremental backup you want to restore
Reads the database history file to give the correct restore sequence 31

32. Redirect Incremental Restore
Restore Incremental backup image first
db2 restore db sample incremental taken at <ts2> redirect
SET TABLESPACE CONTAINERS command
db2 set tablespace containers for 5 using (file '<path>')
CONTINUE command
db2 restore db sample continue
Restore the full backup and incremental after this
db2 restore db mydb incremental taken at <ts1>
db2 restore db mydb incremental taken at <ts2> 32

33. Restore Process Model db2bm Buffer Manipulator
Reads data from buffer and writes to the disk
db2med
Media Controller
reads from the backup image and writes to the buffer
db2agent
Controls the flow between db2bm and db2med 33

34. Restore Performance Tunning
Increase the restore buffer size
Multiple of the backup buffer size specified during the backup operation
Increase the number of buffers
Increase the value of the PARALLELISM parameter
More number of db2bm will be used for write operation
Increase the utility heap size
Tablespaces with multiple containers will benefit from parallel I/O
Multiple page cleaners (db2pclnr) will write data parallely 34

35. Restore Performance Tunning
Increase the restore buffer size
Multiple of the backup buffer size specified during the backup operation
Increase the number of buffers
Value of the PARALLELISM parameter equal to number of tablespaces
One db2bm for each tablespace will be used for write operation
Increase the utility heap size
Tablespaces with multiple containers will benefit from parallel I/O
Multiple page cleaners (db2pclnr) will write data parallely 35

36. Restore Performance Tuning
If no options specified optimal values for number of buffers
buffer size and parallelism are selected automatically
db2diag.log entry shows the values
FUNCTION: DB2 UDB, database utilities, sqluxGetDegreeParallelism, probe:537
DATA #1 : <preformatted>
Autonomic BAR - using parallelism = 14.
FUNCTION: DB2 UDB, database utilities, sqludTuneBuffers, probe:898
Autonomic restore - tuning enabled.
Using buffer size = 3841, number = 14. 36

37. Restore Process Model 37

38. RF Performance Tunning
PREC_NUM_AGENTS
Recovery agents (db2redow)
PREC_NUM_AGENTS=number of online CPUs+1
PREC_NUM_QSETSIZE
Message Queue size
Increase it if you reduce the PREC_NUM_QSETS
PREC_NUM_QSETS
Number of message queues
Decrease the size if PREC_NUM_QSETS is a high value 38

39. RF Performance Tunning
Setting the parameters
Create DB2BPVARS.cfg file with the following details
PREC_NUM_AGENTS=<value>
PREC_NUM_QSETS=<value>
PREC_NUM_QSETSIZE=<value>
db2set DB2BPVARS=<path to file/DB2BPVARS.cfg>
Recycle the instance 39

40. RF Performance Tunning
db2diag.log entry
FUNCTION: DB2 UDB, recovery manager, sqlpAllocatePRCB, probe:2000
DATA #1 : <preformatted>
Using parallel recovery with 9 agents 16 QSets 48 queues and 0 chunks
PREC_NUM_AGENTS=9
PREC_NUM_QSETS=16
PREC_NUM_QSETSIZE=4 40

41. Thank You 41