Master Index Rebuilding in ASE 15.7

(c) 2015 Independent SAP Technical User Group

Annual Conference, 2015

- ISUG TECH 2015- ISUG TECH 2015ConferenceConference

Master Index Rebuilding Master Index Rebuilding Fernando Santos Fernando Santos



AgendaAgendaWelcome Speaker Introduction Parallelism Concept Types of Parallelism Parallelism Best Usage Partitions and Parallelism : CASE Real World &Q A



Fernando Santos Fernando Santos

, , , GLOBAL COE at SAP ASE RepServer . IQ Product Specialist Working at

/ SAP Sybase since 1994



Master Index RebuildingCustomer Scenario

Major Public Bank in Brazil got a problem in his model…

Overflow in a identity column who is the primary key of the bigger tables… ( 1.5 TB) in size

Needed to Rebuild the table and indexes, hole system stopped by 100 hours…

Basic parallelism used with 20 Consumers, but something was wrong

Real World with 50 consumers and producers.



Parallelism Concept



Types of Parallelism



Parallelism – Worker Processes and Merge



Parallelism – Requirements



Partitions and Parallelism



Index Rebuilding using Partitions

Each partition must be scanned by a worker process ( producer)

For each producer must to have a consumer

Time to execute will be related to:-Cache-Disk performance (speed)-Worker process memory



Index Rebuilding – parallelism formula

To use parallelism during create index operation we must to use consumers… create index … on… with consumers=<tasks>

Those consumers depends on 4 configuration params:

Max parallel degreeMax utility parallel degreeNumber of worker processesMemory per worker processes



Index Rebuilding – worker processes setup

To use 20 consumers ( expected to have 41 processes related to execute the command )… create index … on… with consumers=<tasks>

Those params must be set as:

Max parallel degree = 41Max utility parallel degree = 41Number of worker processes = 41 (minimum)Memory per worker processes = 65536Number of sort buffers = 10000



Index Rebuilding – why?

41 processes will be created for 20 consumersEach partition will be scanned by 1 producer process and 1 consumer will be responsible to sort the read

1 process will be the coordinator (sync)

Number of worker processes must to cover all create index/ update statistics running in parallel for different tables

The real number for “number of worker processes” is max parallel degree X < command sessions in parallel>



Index Rebuilding – Real World

Big Table create index with 50 consumers

50 first are producers, each one reading own partition of table50 processes as consumers1 sync process

fid spid status cmd1145 529 sleeping WORKER

PROCESS1145 530 sleeping WORKER PROCESS1145 531 sleeping WORKER PROCESS1145 532 sleeping WORKER PROCESS1145 533 sleeping WORKER PROCESS1145 534 sleeping WORKER PROCESS1145 535 sleeping WORKER PROCESS1145 536 sleeping WORKER PROCESS1145 537 sleeping WORKER PROCESS1145 538 sleeping WORKER PROCESS1145 539 sleeping WORKER PROCESS

1145 1145 sync sleep CREATE INDEX



Index Rebuilding – ProducersSPID LogicalReads PhysicalReads PartitionName529 271618 401 Partition_1530 280399 227 Partition_2531 280344 248 Partition_3532 279316 394 Partition_4533 283772 201 Partition_5534 282586 390 Partition_6535 284095 296 Partition_7536 279560 459 Partition_8537 277726 372 Partition_9538 277901 336 Partition_10

.........SPID LogicalReads PhysicalReads PartitionName574 282646 379 Partition_46575 286800 469 Partition_47576 268046 970 Partition_48577 277900 301 Partition_49578 282327 174 Partition_50

The snapshot shows a create index with 50 consumers

50 first are producers, each one reading own partition of table

The output can be generated by monProcessObject

In this way all scan will go directly to the cache using 4*pagesize pool ( 16K for 2K…)



Index Rebuilding – Consumers

Each consumer can be identified in the same output from monProcessObject

All partition names points to Partition_1 ( or first Partition name)

Don’t see physicalReads, because is a sort and write processing

The performance here depends on cache size, number of sort buffers and Disk Speed I/O for writing operations…

SPID LogicalReads PhysicalReads PartitionName579 514391 0 Partition_1580 220928 0 Partition_1581 377781 0 Partition_1582 589584 0 Partition_1583 230281 0 Partition_1584 299273 0 Partition_1585 288716 0 Partition_1586 77644 0 Partition_1587 132840 0 Partition_1



Index Rebuilding – Customer Results

Caixa Economica Federal – BrazilTable with 1.5 TB Partition by hash – 50 partitionsInitial I/O sub-system = VMAX with SSDFinal I/O sub-system = EMC XTREM I/O



Index Rebuilding – Customer Resultsexecution #1

First Execution-Consumers = 20-Max parallel degree = 21-Worker processes created 21-Problem: 1 producer 20 consumers

All time waiting to sort the data




Second Execution-Consumers = 50-Max parallel degree = 101-Worker processes created 101-Problem: 50 producer (1 for each partition) 50 consumers ( 1 for each producer)

1 sync

Pressure on the I/O subsystem, writing got like 30ms avg svct




Third Execution-Consumers = 50-Max parallel degree = 101-Worker processes created 101-Problem: 50 producer (1 for each partition) 50 consumers ( 1 for each producer)

1 sync

Using EMC XTREM I/O – achieved more then 100,000 IOPS with less than 4 ms per

I/O LIMIT !



Index Rebuilding – Tips and Tricks

•Configure the Default Datacache large pool (16K,64K,128K) for 30%-50% of default pool•Partition the cache as number of engines ( recommended configuration) to be avoid spinlock contention•Setup the I/O sub system, spliting db´s across devices and speed up devices in multiple disks•Adjust max parallel degree, max utility parallel degree, memory per worker processes, number of worker processes and number of sort buffers according your table size and partitions•Use set (sort_resource on and noexec on) at session leve to check the plan of create index before the launch•Setup “max scan parallel degree” for non-partitioned tables using the same formula of “max parallel degree” but take care to do it without production running, could change all plans on the cache… or before adjust “min pages for parallel scan” to a big value… ( never tested yet )



Questions and Answers Questions and Answers



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Master Index Rebuilding in ASE 15.7

Technology

parallelism worker processes

worker process1145

index operation

worker process producer

parallelism requirements

real number

index update statistics

hours basic parallelism