Advanced DBA – High Availability for Data

World®
’16
Advanced DBA – High Availability
for Data
Kevin Shuma
VP, Product Management
CA Technologies
MAINFRAME AND WORKLOAD AUTOMATION
MFX65E

2 © 2016 CA. ALL RIGHTS RESERVED.@CAWORLD #CAWORLD
Abstract
This session describes the available options for sites that need
to keep their CA Datacom data user accessible for extended
periods of time. This include functionality to reorganize,
compress and move data without interrupting user access.
This session will primarily cover the new features available in
the CA Datacom®/DB utility processing that allows users to
continue to access data tables while the DBA is performing
needed database management activities.
Kevin Shuma
CA Technologies
VP, Product
Management

Agenda
WHAT IS HIGH-AVAILABILITY FOR DATA?
FUNCTIONALITY AVAILABLE TO KEEP DATA AVAILABLE
CURRENTLY PLANNED FUNCTIONALITY
SUMMARY
1
2
3
4

What is high-availability?
“High availability is a characteristic of a
system, which aims to ensure an agreed level
of operational performance, usually uptime,
for a higher than normal period.”
“If a user cannot access the system, it is - from
the users point of view – unavailable.
Generally, the term downtime is used to refer
to periods when a system is unavailable.”
According to Wikipedia
24x7

What is high-availability for data?
§ The ability for users to access their data
(tables) anytime the Datacom environment
(MUF) is up
– Do not interrupt user data access for
§ Dataset expansions
§ Data reorganizations
§ Index reorganizations (defragmentation)
§ Index changes (adding or deleting key definitions)
§ Changing compression algorithms
§ DASD restructuring and data row restructuring
§ Just about everything a DBA “does” to manage the system
From a CA Datacom perspective

Functionality available to
keep data available

Dataset expansions
§ CA Datacom supports multiple ways to expand data
and index areas without an outage
– Dynamic extend (dictionary attributes)
§ Can be updated to existing database definitions
§ Provides the MUF the ability to trigger a request for a new
extent when the current extent(s) are full
– On demand extend
§ Console command that triggers a MUF to request a new extent
– Can be placed in a DBUTLTY batch job
§ Does not require dynamic extend to be turned on
We need our data and index areas to expand (for new entries) without an outage

Dataset expansions - Online Area Move process
§ Delivered in V14.01
§ Used for cases where original dataset (index or area)
no longer meets the current need
§ Extents too small – maximum number of dynamic extends being reached
§ Not enough volumes allocated – can only extend on allocated volumes
§ Need to move to a newer, larger, faster DASD device
§ Sites does not want datasets with multiple extents to remain for longer
periods
§ Other needs

Dataset expansions - Online Area Move process (cont’d)
§ Define and PREINIT (DBUTLTY) new “.new” target dataset
– Create with the “new” requirements for extents and volumes
– Same block size as source
§ When ready issue a console command to do
ONLINE_AREA_MOVE
– Opens “.new” dataset to MUF
– Establishes an IO director to manage which dataset has current block
– Begins copy block for block from old dataset to .new
– When done uses an I/O gate to pause the system
§ Scratch or rename current to old and rename “.new” to current

Dataset reorganizations
§ Determine if a reorganization is needed
– Data row reuse allows space in datasets to be reused
§ Default re-use is random (DSOP = 1)
§ New data rows being added may be placed out of (native key) sequence
§ With compression or multi-table areas some fragmentation of free space in
the data blocks may occur
– With good buffering and/or MRDF a lot of the dis-organization is
hidden
– Many reorganizations are done without real need
§ Don’t improve performance or affect fragmentation
We need our data put back into native sequence (for batch performance)

Dataset reorganizations (cont’d)
§ Using the history database (DBID 1007) to determine if
– There is significant sequential (native key) processing

§ Using the history database (DBID 1007) to determine if
– There is significant reduction in sequential efficiency
Re-org
does not
improve
efficiency
Re-org
improves
efficiency

§ Using the DBUTLTY DATANE report to determine if the data is
out of sequence

§ Using the DBUTLTY DATASP report to determine if the data
blocks have a lot of fragmented space

§ Offline Reorg (causes an outage)
– DBULTY BACKUP (SEQ=Native), INIT, LOAD
– DBUTLTY REORG (parallel reorg)
– AREA controls can be used to do just one area of a database
§ Online Reorg
– Triggered by DBUTLTY, but runs in MUF (available for zIIP)
– Allows users to continue to access data
– Moves rows within the existing data area
– Some index space will be used (Moved Record Index)
– Fully recoverable/restart-able
Choosing the right method

§ Online Reorg (cont’d)
– DBUTLTY OLREORG REFGROUP=nn (greater than zero)
§ Reorganizes by moving rows from one block to another
§ Makes sequence “better”
– DBUTLTY OLREORG REFGROUP=0 (Requires DSOP 4 or 5)
§ Reorganizes by moving rows in order to empty blocks
§ Requires a percentage of empty (not in-use) blocks
§ All new blocks are fully loaded
§ Typically results in smaller well organized data table

Index reorganizations (defragmentation)
§ Offline RETIX (causes an outage)
– DBULTY INIT and RETIX of the index
– AREA controls can be used to do just one are of a database
§ Online DEFRAG
– Triggered by DBUTLTY, but runs in MUF (available for zIIP)
– Allows users to continue to access data
– Defragments/combines DXX (low-level) of index
– Reduces in-use blocks, improves performance
– Fully recoverable/restart-able
– Does not reduce “levels”

Index reorganizations (defragmentation) (cont’d)
§ Online DEFRAG (cont’d)
– Low cost, runs in MUF
– Compresses indexes (reduces in-use blocks)
– Improved performance of buffers
Use it freely

Index changes (adding or deleting key definitions)
§ Prior to V15
– Only online ability is through SQL ALTER table
§ Causes significant data row “lock” if large number of rows
§ Not recommended for production
§ Delivered in V15
– Online functionality
§ Ability to remove a key
§ Ability to add a key
Add or removing indexes from existing tables while processing

Index changes (cont’d)
§ Removing a key
– Logically delete a key (index) for a table
§ Internal index still maintained when rows added or deleted
§ Can be re-instated if users detect that the key was needed
– Physically delete a key (index) for a table
§ Locks in logical delete
§ Removes index entries from the index area (IXX or Inn)
– Space available for other indexes to use
Removing indexes from an existing table while processing

§ Adding a new key (index) for a table
– Adds key to Directory CXX
– Key enabled to maintenance commands
– Internal task started to read all rows, add new index
§ When complete key is made available
– Can be added into index –
§ IXX area
§ Existing Inn area (multi-dataset index)
§ Brand new Inn area (multi-dataset index)
Adding indexes to an existing table while processing

§ Swap where a key (index) resides
– Add a parallel key to one being used in
IXX or Inn
– Swap usage for user applications from
old to new
– Delete old key and reclaim space
– Less levels reduces I/O
– Allows COVERED to be much more
effective
§ Cover the specific key IDs that are most
‘time critical’
Moving indexes within an existing table while processing
Multi-dataset index
IXX
I01
I01
IXX

Changing table compression
§ Data row compression can be used to
– Reduce data row footprint (save DASD)
– Improve buffer, memory and zIIP utilization
– Make data less “readable” by external viewers
§ TSO, DITTO, SORT, etc.
§ Online Compress (TA24)
– Allows the DBA to add/remove/change compression
specifications without interrupting user data access
– Full session at CAW 2016 discussing this new capability
Allowing the DBA to change compression with out a data access outage

Other changes in V15
§ MUF RESTART in parallel, much faster
§ Dynamic and directed extend VIRTUAL base area
– Includes the CBS index
– Includes the TTM index
§ Extend the log area LXX
§ Extend the Directory CXX
§ Unique Row Identifier (URI) reuse
Removing MUF outages that affect user data access

Currently planned functionality

Under Consideration
§ ONLINE_AREA_RELEASE
– Free unused/never used space at back of dataset
§ Data area only
– In a second can release space back to system
§ Past Maximum used blocks
§ Past High Used Block
§ Good for areas that were oversized at INIT
Items that are in the current backlog of new functionality

Under Consideration (cont’d)
§ ONLINE Block Size Alter (Pre-initialize a new data area
– Part ONLINE_AREA_MOVE, Part OLREORG
§ Pre-initialize a new data area
– “Right-sized” extents
§ Different block size
§ Datadictionary driven
§ Moves rows by native key to new area
– Any ADDIT during also goes to current block so not in order
§ When done old area scratched, new area renamed

Under Consideration (cont’d)
§ ONLINE_TABLE_MOVE
– Part ONLINE_AREA_MOVE and part OLREORG
§ Pre-initialize a new data area
– “Right-sized” extents
§ Imagine old area 1000 cylinders but currently 1 record on last track
– New area can be 2 tracks and will run very fast
§ Moves rows by native key to new area
– Any ADDIT during also goes to current block so not in order
§ When done old area scratched, new area renamed

Summary
A Few Words to Review
Experiences
One site has used these new
functions to keep their user
data available 24x7 for over 4
years.
Key Topics
In today’s world, user’s data
must be accessible 24x7
Findings
CA Datacom continues to
deliver new functionality that
allows the DBA to perform
needed activities without
interrupting user access.

@CAWORLD #CAWORLD © 2016 CA. All RIGHTS RESERVED.30 @CAWORLD #CAWORLD © 2016 CA. All RIGHTS RESERVED.30
Mainframe and Workload Automation
For more information on Mainframe and Workload Automation,
please visit: http://cainc.to/9GQ2JI

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The content provided in this CA World 2016 presentation is intended for informational purposes only and does not form any type of
warranty. The information provided by a CA partner and/or CA customer has not been reviewed for accuracy by CA.
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Advanced DBA – High Availability for Data

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