IBM Software Group ® Backup & Recovery. IBM Software Group | DB2 Information Management Software Agenda Backup Types Backup Process Model Backup

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


Backup

Backup Types Online or Offline

Database Level backup or Tablespace Level backup

Full, Incremental or Delta


Offline Backup

Database needs to be offline

Internally establishes connection to the specified database

Faster than online

Default option


Online Backup

Database is accessible

Needs archival logging enabled

Slower than offline backup

Log files are included by default

Incremental and delta


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


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


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



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



db2bm

Controlled by PARALLELISM option

Reads data from disk into backup buffer

Sends full buffer message on the full queue for db2med



db2bm

Function stack trace while waiting for the next available buffersqluReadAdrFromQueuesqlubGetNextBuffer

Function stack trace while readingpread64sqloReadBlocks

Function stack trace after completing reading datasqluReadMessageFromQueuesqlubbuf



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



db2med

Function stack trace while waiting for full buffer notificationsqluReadAdrFromQueuesqluMCContinueBackup

Function stack trace while writingwritesqlowrite



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



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



db2med with TSM

db2vend process used

db2med invokes the TSM code inside db2vend



db2vend

Independent process to execute the vendor API code

Similar to db2fmp

Runs outside DB2 address spacePrevents unexpected API errors from crashing DB2


Backup Performance Tuning

Backup command options

WITH num-buffers BUFFERS

PARALLELISM n

BUFFER buffer-size



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



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.



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



Fragmentation

db2bm reads contiguous blocks of data

Fragmentation due free extents can affect performance

REORG should be done to reduce fragmentation



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



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




Restore

Restore Types Full database restore

Tablespace restore

Redirect restore

Incremental Restore


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


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


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


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


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


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>



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



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



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


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.




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



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



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


Thank You

Documents

IBM Software Group ® Backup & Recovery. IBM Software Group | DB2 Information Management Software Agenda Backup Types Backup Process Model Backup