Sql server 2014 online operations

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EVENT

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Online Database OperationsSQL Server 2014Antonios Chatzipavlis

Database Architect • SQL Server Evangelist • Trainer MCT, MCSE, MCITP, MCPD, MCSD, MCDBA, MCSA, MCTS, MCAD, MCP, OCA, ITIL-F

Feb 26, 2015

53

I have been started with computers.

I started my professional carrier in computers industry.

I have been started to work with SQL Server version 6.0

I earned my first certification at Microsoft as Microsoft Certified Solution

Developer (3rd in Greece) and started my carrier as Microsoft Certified

Trainer (MCT) with more than 20.000 hours of training until now!

I became for first time Microsoft MVP on SQL Server

I created the SQL School Greece (www.sqlschool.gr)

I became MCT Regional Lead by Microsoft Learning Program.

I was certified as MCSE : Data Platform, MCSE: Business Intelligence

Antonios ChatzipavlisDatabase Archi tect

SQL Server Evange l i st

MCT, MCSE, MCITP, MCPD, MCSD, MCDBA,

MCSA, MCTS, MCAD, MCP, OCA, ITIL-F

1982

1988

1996

1998

2010

2012

2013

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[email protected]

CHAPTER

Managed Lock Priority

53th AUTOEXEC.GR Event / 2nd PASS Greek Chapter Event

• Blocking transactions need to be completed before DDL

• SWITCH/OIR will block new transactions

• Workload slow down or timeouts

• Impact to Tier1 mission-critical OLTP workloads

Partition SWITCH

• Short Sch-M lock on source and target tables

Online Index Rebuild (OIR)

• Short table S and Sch-M lock

Problem statement


Lock queueSession

Wait

Grant

51-SELECT

52-DDL

53-SELECT

54-SELECT

55-SELECT First in first out

Behavior without Managed Lock Priority


• Blocking user transactions killed

• Immediately or after specified wait time

• MAX_DURATION* = n minutes

• Wait for blockers

• MAX_DURATION*

• Regular lock queue

• Blocking user transactions killed

• Immediately or after specified wait timeMAX_DURATION* = n minutes

LOW PRIORITY LOCK QUEUE

*If there are no blockers, lock is granted immediately

and the DDL statement will complete successfully

Managed Lock Priority Options


Sch-M lock (source and destination)

Blocking by user transactions

Killed at source and destination tables

PARTITION SWITCH

Managed by DBA for both partition switch and OIR

Lock request placed in lower priority queue

Decision to wait or kill self or blockers

Executed immediately if no blockers

BENEFITS

MAX_DURATION applies to every lock request

Time reset for every S and Sch-M lock

Only Sch-M lock conflict for read-only workload

ONLINE INDEX REBUILD

Managed Lock Priority SWITCH/OIR details


Lock queueSession

Low Priority Wait

Grant

51-SELECT

52-DDL

53-SELECT

54-SELECT

55-SELECT

Behavior with Managed Lock Priority


• ABORT_AFTER_WAIT=BLOCKERS all blocking user transactions killed

• ALTER ANY CONNECTION server-wide permission

ALTER TABLE

• Requires ALTER permission on the table

• Applies to both source and target tables

• Switched data inherits the security of the target table

ALTER INDEX

• ALTER permission on the table or view is required

Permissions and security


• Abort session diagnostics

• Deadlock diagnostics in deadlock graph

• sys.dm_tran_locks

“request_status”

extensions

LOW_PRIORITY_CONVERT,

LOW_PRIORITY_WAIT, or

ABORT_BLOCKERS

• sys.dm_os_wait_stats

“wait_type” extensions

…LOW_PRIORITY and

…ABORT_BLOCKERS

• lock_request_priority_state

• process_killed_by_abort_blockers

• ddl_with_wait_at_low_priority

Diagnostics

DEMO

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Partitions

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Single Partition Online Index Rebuild


• Timeouts or workload slow down

• Heavy resource usage (CPU, disk, memory)

• Transaction log bloat

• Impact to mission-critical workloads

• Rebuild online (entire index for a partitioned table)

• Rebuild offline (a selected partition)

• Table locked exclusively (with Sch-M lock) for the entire duration

Problem statement


Granularity

Accessibility

Lock Priority

One or more partitions

Table accessible for DML and query operations

Short-term locks at beginning and end of index rebuild

Uses Managed Lock Priority with SPOIR

Availability Reduces downtime for mission-critical workloads

Resource savingsCPU, memory, and disk space

Reduces log space usage

SPOIR benefits


• Error 155 removed

• “ONLINE” is now a recognized ALTER INDEX REBUILD PARTITION option

• Shows partition info

• For partition #4: OIR DDL plan shows:

-- Constant Scan(VALUES:(((4))))

• sqlserver.progress_report_online_index_operation

• Two new data fields:

• partition_number: ordinary number of the partition being built

• partition_id: ID of the partition being built

Diagnostics


• SMO interface for MLP/SPOIR is supported, including

scripting

• PowerShell is supported

• SSMS• MLP SWITCH is supported through scripting

• No UI support for online index operations

Manageability

DEMO

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Indexes


ABORT_AFTER_WAIT=BLOCKERS

Locking

DDL Transaction

Long running queries and transactions

May not be beneficial in workloads with short transactions

SWITCH acquires locks on source and target tables

Wait on the second lock affects concurrency on first lock

Dormant tables

Nested transaction holds locks longer

Transaction log growthLog truncation affected by MAX_DURATION

Extra logging OIR DDL operation

May lead to system performance issue

Best practices

Sql server 2014 online operations

Technology

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