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IBM Software Group
®
Backup & Recovery
IBM Software Group | DB2 Information Management Software
Agenda
Backup Types
Backup Process Model
Backup Performance Tunning
Restore Types
Restore Process Model
Restore Performance Tunning
RollForward Performance Tunning
IBM Software Group | DB2 Information Management Software
Backup
Backup Types Online or Offline
Database Level backup or Tablespace Level backup
Full, Incremental or Delta
IBM Software Group | DB2 Information Management Software
Offline Backup
Database needs to be offline
Internally establishes connection to the specified database
Faster than online
Default option
IBM Software Group | DB2 Information Management Software
Online Backup
Database is accessible
Needs archival logging enabled
Slower than offline backup
Log files are included by default
Incremental and delta
IBM Software Group | DB2 Information Management Software
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
IBM Software Group | DB2 Information Management Software
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
IBM Software Group | DB2 Information Management Software
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
IBM Software Group | DB2 Information Management Software
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
IBM Software Group | DB2 Information Management Software
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
IBM Software Group | DB2 Information Management Software
Backup Process Model
db2bm
Function stack trace while waiting for the next available buffersqluReadAdrFromQueuesqlubGetNextBuffer
Function stack trace while readingpread64sqloReadBlocks
Function stack trace after completing reading datasqluReadMessageFromQueuesqlubbuf
IBM Software Group | DB2 Information Management Software
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
IBM Software Group | DB2 Information Management Software
Backup Process Model
db2med
Function stack trace while waiting for full buffer notificationsqluReadAdrFromQueuesqluMCContinueBackup
Function stack trace while writingwritesqlowrite
IBM Software Group | DB2 Information Management Software
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 notificationsqluReadMessageFromQueueSqluxReadAgentQueuesqlubcka
IBM Software Group | DB2 Information Management Software
Backup Process Model
Message queues.
Communication between db2agent, db2bm and db2med is managed by message queues
Following message queues created1 message queue for the db2agent1 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
IBM Software Group | DB2 Information Management Software
Backup Process Model
db2med with TSM
db2vend process used
db2med invokes the TSM code inside db2vend
IBM Software Group | DB2 Information Management Software
Backup Process Model
db2vend
Independent process to execute the vendor API code
Similar to db2fmp
Runs outside DB2 address spacePrevents unexpected API errors from crashing DB2
IBM Software Group | DB2 Information Management Software
Backup Performance Tuning
Backup command options
WITH num-buffers BUFFERS
PARALLELISM n
BUFFER buffer-size
IBM Software Group | DB2 Information Management Software
Backup Performance Tuning
Backup command options
WITH num-buffers BUFFERSUse at least twice as many buffers as backup sessionswhich will not cause the target devices to wait for data
PARALLELISM nNumber of processes that are started to read data from thedatabaseSet n equal to the number of tablespaces being backed up
BUFFER buffer-sizeBuffer-size is a multiple of the table space extent size plus one
page
IBM Software Group | DB2 Information Management Software
Backup Performance Tuning
If no options specified optimal values for number of buffersbuffer size and parallelism are selected automatically
db2diag.log entry shows the values that are selected
FUNCTION: DB2 UDB, database utilities, sqluxGetDegreeParallelism, probe:537DATA #1 : <preformatted>Autonomic BAR - using parallelism = 10.
FUNCTION: DB2 UDB, database utilities, sqlubTuneBuffers, probe:898DATA #1 : <preformatted>Autonomic backup - tuning enabled.Using buffer size = 4481, number = 10.
IBM Software Group | DB2 Information Management Software
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
IBM Software Group | DB2 Information Management Software
Backup Performance Tuning
Fragmentation
db2bm reads contiguous blocks of data
Fragmentation due free extents can affect performance
REORG should be done to reduce fragmentation
IBM Software Group | DB2 Information Management Software
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
IBM Software Group | DB2 Information Management Software
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
IBM Software Group | DB2 Information Management Software
Backup Process Model
IBM Software Group | DB2 Information Management Software
Restore
Restore Types Full database restore
Tablespace restore
Redirect restore
Incremental Restore
IBM Software Group | DB2 Information Management Software
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
IBM Software Group | DB2 Information Management Software
Redirect Restore
Issue RESTORE command with REDIRECT optiondb2 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 optiondb2 restore db sample continue
IBM Software Group | DB2 Information Management Software
Redirect Restore Automatic Storage
Use ON option to set the path for automatic storage tablespacesdb2 restore db sample on <path> redirect
If no normal tablespaces then CONTINUE commanddb2 restore db sample continue
IBM Software Group | DB2 Information Management Software
Incremental Restore
Identify and restore the last incremental backup imageThis 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 againThis time the actual data will be restored
IBM Software Group | DB2 Information Management Software
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
IBM Software Group | DB2 Information Management Software
Redirect Incremental Restore
Restore Incremental backup image firstdb2 restore db sample incremental taken at <ts2> redirect
SET TABLESPACE CONTAINERS command db2 set tablespace containers for 5 using (file '<path>')
CONTINUE commanddb2 restore db sample continue
Restore the full backup and incremental after thisdb2 restore db mydb incremental taken at <ts1>db2 restore db mydb incremental taken at <ts2>
IBM Software Group | DB2 Information Management Software
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
IBM Software Group | DB2 Information Management Software
Restore Performance Tunning
Increase the restore buffer sizeMultiple of the backup buffer size specified during the backup
operation
Increase the number of buffers
Increase the value of the PARALLELISM parameterMore number of db2bm will be used for write operation
Increase the utility heap size
Tablespaces with multiple containers will benefit from parallel I/OMultiple page cleaners (db2pclnr) will write data parallely
IBM Software Group | DB2 Information Management Software
Restore Performance Tunning
Increase the restore buffer sizeMultiple 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/OMultiple page cleaners (db2pclnr) will write data parallely
IBM Software Group | DB2 Information Management Software
Restore Performance Tuning
If no options specified optimal values for number of buffersbuffer size and parallelism are selected automatically
db2diag.log entry shows the values
FUNCTION: DB2 UDB, database utilities, sqluxGetDegreeParallelism, probe:537DATA #1 : <preformatted>Autonomic BAR - using parallelism = 14.
FUNCTION: DB2 UDB, database utilities, sqludTuneBuffers, probe:898DATA #1 : <preformatted>Autonomic restore - tuning enabled.Using buffer size = 3841, number = 14.
IBM Software Group | DB2 Information Management Software
Restore Process Model
IBM Software Group | DB2 Information Management Software
RF Performance Tunning
PREC_NUM_AGENTSRecovery agents (db2redow)PREC_NUM_AGENTS=number of online CPUs+1
PREC_NUM_QSETSIZEMessage Queue size Increase it if you reduce the PREC_NUM_QSETS
PREC_NUM_QSETSNumber of message queuesDecrease the size if PREC_NUM_QSETS is a high value
IBM Software Group | DB2 Information Management Software
RF Performance Tunning
Setting the parameters
Create DB2BPVARS.cfg file with the following detailsPREC_NUM_AGENTS=<value>PREC_NUM_QSETS=<value>PREC_NUM_QSETSIZE=<value>
db2set DB2BPVARS=<path to file/DB2BPVARS.cfg>
Recycle the instance
IBM Software Group | DB2 Information Management Software
RF Performance Tunning
db2diag.log entry
FUNCTION: DB2 UDB, recovery manager, sqlpAllocatePRCB, probe:2000DATA #1 : <preformatted>Using parallel recovery with 9 agents 16 QSets 48 queues and 0 chunks
PREC_NUM_AGENTS=9PREC_NUM_QSETS=16PREC_NUM_QSETSIZE=4
IBM Software Group | DB2 Information Management Software
Thank You
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