Defy Murphy's Law with DB2 Backup and Restore - Act … Murphy's Law with DB2 Backup and...Defy...

Defy Murphy's Law with DB2 Backup and Restore

3 March 2011

© Copyright 3/4/2011 BMC Software, Inc 2

Murphy's Law ("If anything can go wrong, it will") was born at Edwards Air Force Base in 1949 at North Base.

It was named after Capt. Edward A. Murphy, an engineer working on Air Force Project MX981, (a project) designed to see how much sudden deceleration a person can stand in a crash.

One day, after finding that a transducer was wired wrong, he cursed the technician responsible and said, "If there is any way to do it wrong, he'll find it.“

"If there's more than one way to do a job, and one of those ways will result in disaster, then somebody will do it that way.“


Agenda

Making sure everything is copied and well taken care of - Listdef, template switching, scope(pending)

Making sure the copied data is usable - Checkpage; Copytocopy; Objects in error; avoiding specific Image Copy

Keep the DB2 Catalog Manageable- MODIFY RECOVERY

Is everything OK for and during recovery - Report Recovery Display progress of Recover in LOGAPPLY phase

Is point in time recovery again a feasible option - RECOVER PIT with Consistency

Don´t challenge Murphy - Some things to be prepared (watch out) for - Tables that contain identity columns- Not logged objects- Recover Clone(d) objects


COPY LISTDEF

LISTDEF will automatically pull in new objects if wildcard chars are used- Related sets of objects

Well defined data set names for templates will automatically handle the creation of output image copy data sets- Ensure unique data set names with substitution variables

Templates will automatically define the GDG base for new objects

Let Utility calculate the dasd space requirements for the template datasets

TEMPLATE LP

UNIT SYSALLDA

MODELDCB model GDGLIMIT(60)

DSN &DB..&SN..&IC..&LR..&PB..P&PA..(+1)


LISTDEF – Considerations

Exclude a partition - the only way to exclude a partition is if it was first included explicitly as a partition

– YES :LISTDEF LST1 INCLUDE TABLESPACE DB.TS1 PARTLEVEL

EXCLUDE TABLESPACE DB.TS1 PARTLEVEL(7)

– NO : LISTDEF LST2 INCLUDE TABLESPACE DB.TS1

EXCLUDE TABLESPACE DB.TS1 PARTLEVEL(7)

Limitation : not permissible to create all-inclusive lists- DATABASE * - TABLESPACE *.*.

The RI parameter can be included on the INCLUDE - RI parameter cannot be used in conjunction with PARTLEVEL


LISTDEF – more considerations

If CLONE Keyword (or Option) exists - Utility will operate against BASE by default

LISTDEF - INCLUDE and EXCLUDE for both BASE and CLONE

Utility will only process BASE or CLONE objects - Example

LISTDEF final list 100 Objects 5 of them have clones Final list used with COPY without CLONE keyword

– 100 Base objects will be copied

Final list used with COPY with CLONE keyword specified– 5 Clone objects will be copied


LISTDEF Warnings….

RI and PARTLEVEL are mutually exclusive

Object restriction still apply!! No selection on status ( see later)

LIST is NOT re-evaluated at restart time- objects could have been dropped or created


COPY – Template Switching

Template switching - copy to tape if large; to disk if small

Only supported for image and inline copies

- (COPYDDN, RECOVERYDDN);

- LIMIT is ignored if the TEMPLATE on which it is specified is used for other purposes (e.g.WORKDDN, PUNCHDDN)

TEMPLATE BIG DSN &DB..&TS..D&DA..T&TI. UNIT=TAPE

TEMPLATE SMALL DSN &DB..&TS..D&DA..T&TI. UNIT=SYSALLDA LIMIT(20 CYL, BIG)

COPY TABLESPACE SMALL.TS COPYDDN(SMALL)

COPY TABLESPACE LARGE.TS COPYDDN(SMALL)


COPY – Template Switching

The decision to switch is made based on the ESTIMATED output data set size- which may differ from the actual final size of the output data set.

- for incremental image copies estimated at 10% of the space required for a full image copy.

Remember - constrain and quantify the allocation extents

- PCTPRIME – 100% or required space is alllocated as PRIMARY- MAXPRIME – upperlimit value (not percentage)- NBRSECND – number of secondary extents


COPY – SCOPE(PENDING)

Objects listed will only be copied if in:- COPY pending status- ICOPY pending status

If DSNUM(ALL) is specified - if any of the partitions are in COPY or ICOPY, all of the partitions will be copied

Not Logged objects- Only SHRLEVEL(REFERENCE) copies are allowed

PBG (partition by growth) table spaces- SHRLEVEL(CHANGE) copy at the table space level will copy partitions that are grown while

the copy is running


COPY – CHECKPAGE

Since DB2 9 always CHECKPAGE

no longer sets copypending, so…. Check those RCs!

new SYSCOPY record type is written if a broken page is detected to force a full image next since dirty bits may have already been flipped off in the space map pages

- TTYPE column, with a value of “B” (ICTYPE = T)


COPYTOCOPY Utility

Use a LISTDEF list with templates for the output datasets

Does not support parallelism, but sorts, then processes the objects based on: Input image copies‟ tape stack(s) Output image copies‟ tape stack(s) Size – ascending order

- For tapes, minimizes mounts/demounts/rewinds automatically

Not possibel for Concurrent Copies

Does not support - DSNDB01.SYSUTILX and its indexes - DSNDB01.DBD01 and its indexes - DSNDB06.SYSCOPY and its indexes


COPYTOCOPY Utility:

Output image

copy stack for RP:

fsn=1 WILDLIFE.MOUSE

fsn=2 WILDLIFE.BEAVER

fsn=3 WILDLIFE.BEAR

fsn=4 WILDLIFE.HIPPO

fsn=5 WILDLIFE.SQUIRREL

fsn=6 WILDLIFE.LYNX

fsn=7 WILDLIFE.TIGER

fsn=8 WILDLIFE.ELEPHANT

Sorted by input image

copy stack 2:

WILDLIFE.SQUIRREL

WILDLIFE.LYNX

WILDLIFE.TIGER

WILDLIFE.ELEPHANT

Sorted by input image

copy stack 1:

WILDLIFE.MOUSE

WILDLIFE.BEAVER

WILDLIFE.BEAR

WILDLIFE.HIPPO

WILDLIFE.BEAR

WILDLIFE.BEAVER

WILDLIFE.ELEPHANT

WILDLIFE.HIPPO

WILDLIFE.LYNX

WILDLIFE. MOUSE

WILDLIFE.SQUIRREL

WILDLIFE.TIGER

LISTDEF ANIMALS

INCLUDE TABLESPACES DATABASE WILDLIFE

COPYTOCOPY LIST ANIMALS

FROMLASTFULLCOPY RECOVERYDDN(RP)


Avoiding Specific Copy

Recover RESTOREBEFORE x‟rba/lrsn‟

Directs the Recover Utility to use a recovery base prior to the rba or lrsn specified

Mutually exclusive with TOCOPY, TOLASTCOPY, or TOLASTFULLCOPY.


COPY INDEXES

Options event(itemerror,skip) and copy shrlevel(change)- Keeps objects in the list in UTRW state *only* as each object is being copied instead of for the

duration of the Copy Utility

Specifying OPTIONS EVENT(ITEMERROR,SKIP)

UTRW – utility allows read/write access by applications, but no access for exclusive utilities


COPY INDEX – Informational COPY-pending status

Setting and clearing the informational COPY-pending status

Index with COPY YES attribute the following utilities can place the index in the informational COPY-pending (ICOPY) status set by:

- REORG INDEX - REORG TABLESPACE LOG YES or NO - LOAD TABLE LOG YES or NO - REBUILD INDEX


MODIFY RECOVERY

Specify what is to be retained instead of what is to be deleted

Instead of DELETE parameter - Date or AGE

Code a RETAIN parameter


MODIFY RECOVERY – RETAIN LAST

Deletion works on dates and not on timestamps.- As a result, more entries than requested might be kept.

Example, - Five most recent copies were taken on the same day - RETAIN LAST(2) is specified- Records for all five copies that were taken on that day are retained in SYSCOPY


MODIFY RECOVERY

Keep SYSCOPY and SYSLGRNX in a manageable state

REORG SYSIBM.SYSCOPY and SYSIBM.SYSLGRNX regularly- If timeout or deadlock is received while deleting syslgrnx records, we commit what has been

done so far - Next run of Modify Recovery will pick up where the previous run left off

Indexes with the COPY YES attribute processed automatically- Index recovery is dependent on recovery information for the underlying table space

Will remove records from SYSIBM.SYSLGRNGX without removing SYSIBM.SYSCOPY


MODIFY RECOVERY – GDGLIMIT

Full image copies using one GDG and incremental image copies using a separate GDG

The date and time of creating the image copy are (not) visible in data set- only in SYSIBM.SYSCOPY


Report Recovery Information

Information about the image copy data sets and archive log data set that might be required during the recovery.

Three sections

- Recovery history from the SYSIBM.SYSCOPY catalog table Including information about any system level backup copies that can be used for an object

level recovery. - Log ranges from SYSIBM.SYSLGRNX.

- Volume serial numbers where archive log data sets from the BSDS reside.

-


Report Recovery Information

Example Example


Display Progress of Recover LOGAPPLY phase

To help see progress and estimate elapsed time

Progression of Recover logapply shown via –DIS UTIL command- only issued during RECOVER LOGAPPLY phase

DSNU116I csect-name RECOVER LOGAPPLY PHASE DETAILS:

STARTING TIME = timestamp

START RBA = ss START LRSN = rr

END RBA = ee END LRSN = nn

LAST COMMITTED RBA = cc LAST COMMITTED LRSN = ll

ELAPSED TIME = hh:mm:ss


Recover on a LISTDEF list with PARALLEL

Build LISTDEF lists for sets of related objects

Parallelism in the RESTORE phase…objects are sorted by:- Device type of image copy(s)

DASD Tape – objects sorted to avoid mounts/demounts/rewinds

– File sequence number– Volser(s)

- Size – ascending order- Type of image copy

DB2 image copy Concurrent copy

Do not mix objects to be restored from image copies and objects to be restored

from concurrent copies in the same RECOVER Utility statement


RECOVER – Parallelism

RESTORE phase : PARALLEL(n) keyword TAPEUNITS(n) keyword

- For image copies on tape - consider full + incremental copies- System limit for threads- Storage in the batch Utility address space- Restore of some objects will be deferred if there is a problem with the image copies

LOGAPPLY phase (fast logapply) :- 98 subtasks to apply the log records

Each subtask handles a table space or partition Depends on the mix of log records in the current log read buffer Log records sorted by dbid, psid, partition number, page number

LISTDEF ANIMALS

INCLUDE TABLESPACES DATABASE WILDLIFE

RECOVER LIST ANIMALS

PARALLEL(4)


Recover to any point in time (PIT)

With consistency

- Uncommitted changes are backed out

- Significantly reduces (eliminates?) the need to run QUIESCE which can be disruptive to applications

- Does not apply to RECOVER TOCOPY, TOLASTCOPY and TOLASTFULLCOPY using SHRLEVEL CHANGE copy (consistency is not ensured – use RBA/LRSN after COPY point)

- Include all relevant objects in same RECOVER to ensure data consistency from the application point of view


Recover to any point in time (PIT)

With consistency – TOLOGPOINT or TORBA

LOGAPPLY phase – applies log records to the recovery point specified

Introduced new log phases

– LOGCSR – analyzes URs active at the recovery point– LOGUNDO – rolls back uncommitted changes


Recovering to a point in time with consistency

RECOVER TOLOGPOINT and TORBA have recover with consistency as its default behavior.

No consistency is ensured if - RECOVER TOCOPY, TOLASTCOPY, and TOLASTFULLCOPY using SHRLEVEL CHANGE

To achieve consistency with a recovery to a SHRLEVEL CHANGE copy- Use a desired SHRLEVEL CHANGE copy as the recovery base - Specify a recovery point that was right after the copy completed via the TORBA or

TOLOGPOINT syntax.- Locate the entry in the SYSCOPY table for the SHRLEVEL CHANGE copy that is being used

and use the RBA or LRSN value in the PIT_RBA column as the recovery point

Use the REPORT RECOVERY utility to see the report of the SYSCOPY records


Recovering tables that contain identify columns

Column attribute AS IDENTITY

When recovering a table that has an identity column to a point in time, you can create a gap in the identify column values. When you insert a row after this recovery, DB2 produces an identity value for the row as if all previously added rows still existed.

CREATE TABLE EMPL

(EMPNO INTEGER GENERATED ALWAYS AS IDENTITY,

INSERT

INSERT

INSERT

EMPL 1 1 1 1

2 2 2 2

3 3 3 3

4 7

5 8

6 9

IMAGE COPY INSERT

INSERT

INSERT

RESTORE IC INSERT

INSERT

INSERT


30

Recovery of Objects in Error

-DISPLAY DB(*) SPACE(*) LIMIT(*) RESTRICT- COPY, LPL, WEPR, GRECP.

-DISPLAY DB(*) SPACE(*) LIMIT(*) ADVISORY- ICOPY, AUXW, and AREO*.

-DISPLAY DB(*) SPACE(*) LPL ONLY


Recoverability of Not Logged objects

Say what ?

Not Logged objects can only be recovered to a point in time that is a “recoverable point”

- Object will be recovered to the most recent “recoverable point”:

Alter to Not Logged Image copy taken with SHRLEVEL(REFERENCE) made while Not Logged


NOT LOGGED Table Spaces – Catalog Changes

LOG column of SYSIBM.SYSTABLESPACE reflects - non-LOB table spaces as well as LOB table spaces.

• Possible values are:– „Y‟, LOGGED.– „N‟, NOT LOGGED.– „X‟, NOT LOGGED, linked to the base.

SYSLGRNX records are not maintained for NOT LOGGED table spaces.

SYSCOPY records are written for the following events. When a table space is created as LOGGED; ICTYPE='C„ STYPE='L' When a table space is created as NOT LOGGED; ICTYPE='C„ STYPE=„O‟ When a table space is altered to LOGGED; ICTYPE='A„ STYPE='L' When a table space is altered to NOT LOGGED; ICTYPE='A' STYPE='O„

- The LRSN in these SYSCOPY records reflects the point in the log at which the logging attribute was altered.

- A new column, LOGGED, is added to the SYSCOPY Catalog table. Values can be: „Y‟ - indicates the LOGGED attribute. „N‟ - indicates the NOT LOGGED attribute. blank - indicates that the row was inserted prior to V9.

- 32 -


Recover of CLONED Objects

Base and clones objects must be recovered in separate Recover Utility statements

May recover fully (to current) even when the recovery base is before EXCHANGE DATA

Recovery to point in time prior to EXCHANGE DATA is not allowed


COPY/RECOVER – To Remember

MODIFY Recovery enhancements- “Retain” keyword added to improve management of copies

LAST(n), LOGLIMIT, GDGLIMIT

RECOVER to any point-in-time with consistency

RECOVER RESTOREBEFORE to use an earlier image copy

Display progress of RECOVER during log apply

COPY CHECKPAGE option always active- “Copy Pending” avoided if broken page encountered

COPY SCOPE PENDING - to copy only objects in “Copy Pending”

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