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SAP HANA Database Server Management Console (hdbcons) Interview Question and answer

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SAP HANA Database Server Management Console (hdbcons) Interview Question and answer
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FAQ HANA DB Server Management Console (hdbcons)

1. What is the SAP HANA database server management console?

The SAP HANA database server management console (hdbcons) is an expert tool delivered as part of the SAP HANA software. In normal cases it is not required to use it, but in some scenarios you can take advantage of its functionalities.

As impromper usage of hdbcons can have a severe impact on SAP HANA, you should only run it under guidance of SAP (e.g. if recommended in a SAP incident or SAP Note).

2. How can hdbcons be started?

The following alternatives exist to start hdbcons:

Tool Details
Direct call (Linux level)

On Linux level you can start hdbcons via:

hdbcons [-p <pid>] [-e <process_name>]

Per default hdbcons will connect to the indexserver process, but you can specify the process ID of another SAP HANA process via "-p <pid>" or the name of another SAP HANA process via "-e <process_name>" (e.g. <process_name> = 'hdbnameserver').

SAP HANA Studio

Per default the database console isn't displayed, but you can change it via:

Window
-> Preference
-> Global Settings
-> Show Management Console for hdbcons

Subsequently you will find an hdbcons input section at:

Systems
-> Administration
-> Console

SQL

You can start hdbcons commands via SQL using:

CALL MANAGEMENT_CONSOLE_PROC('<hdbcons_command>', '<host>:<port>', ?)

<hdbcons_command> can contain any hdbcons command, e.g. the ones listed in "What are the most important hdbcons functionalities" below.

3. Where do I find an overview about available hdbcons functionalities?

The following commands can be used in hdbcons to display an overview of hdbcons functionalities:

Command Details
hdbcons help Overview of available server related options
hdbcons help <command>  
hdbcons -? Overview of available client related options

4. What are the most important hdbcons functionalities?

The following table provides and overview about some hdbcons functionalities. Several of the 'mm' calls can be extended by the '-r' switch so that they apply also to sub-allocators of the specified heap allocator <allocator>.

Command  Document Details
context l -s

1827393
1999020

Generate call stacks for active threads

crypto ssfs resetConsistency

2097613

Reset SSFS consistency

distribute e <host>:<port> <command>

2146984

Execute hdbcons command <command> on remote node identified via <host>:<port>

event acknowledge -t <type>

2147247

Acknowledge internal events of type <type>

help <command>

 

Provide further details for a specific hdbcons command <command> (e.g. 'mm')

log backup

2106240

Force log backup

log release

1995412

Release free log segments

mm bl -t <allocator>

1999997

List the top contributors to the memory allocation of a specific heap allocator <allocator>

mm cg -o <file>.dot <allocator>

1786918
1999997

Generate output file with allocator stack trace information for heap allocator <allocator>

mm f <allocator> as

1786918
1999997

Activation of allocator call stack trace for <allocator>

mm f <allocator> as -d

1786918
1999997

Deactivation of allocator call stack trace for <allocator>

mm gc [-f]

1999997

Return free memory to the operating system ('-f' to consider also free fragments in big blocks)

mm l -s -S -p

1786918

Print general heap allocator list with some statistics ('-s'), sorted by total size descending (-S) and peak usage statistics (-p)

mm ru

1999997

Reset all previous memory measurements ("reset usage")

mm top -l <num> <allocator>

1999997

Generate report with top <num> call stacks recorded for heap allocator <allocator>

pageaccess a

1999997

Provide breakdown of Pool/PersistenceManager/PersistentSpace(0)/DefaultLPA/Page content based on page type

profiler clear

1804811

Reset kernel profiler trace
profiler print -o <file>.dot

1813020

Generate a kernel profiler trace output file <file>.dot
profiler start

1813020

Start a kernel profiler trace
profiler stop

1813020

Stop a kernel profiler trace
replication i

2063657
2086024

Overview of system replication information
resman minswappable -s 0

1970537

Overwrite inadequate unload_lower_bound settings during recovery

resman s -s <size_gb>G

2146989

Shrink memory allocation to <size_gb> GB if possible

runtimedump dump

1813020

Generate a runtime dump

savepoint execute

2228171

Trigger a savepoint

snapshot a <snapshot_id>

1999880

Analyze SAP HANA snapshot (<snapshot_id> can be retrieved via "snapshot l")

snapshot d <snapshot_id>

1999880
2100009

Delete SAP HANA snapshot (<snapshot_id> can be retrieved via "snapshot l")

snapshot l

1999880

List SAP HANA snapshots

statreg print -n <monitor_view_name>

SAP HANA Troubleshooting Guide

Print content of monitor view <monitor_view_name>

tablepreload c [-f]

2127458

Print column preload information ('-f' for full information)

tablepreload w [-s]

1889081
2107959
2127458

Persist preload information based on columns currently loaded in memory ('-s' for synchronous write)

Read here for more SAP HANA Interview Questions

Read here Perspectives of SAP HANA Studio

Read here Steps to Add New HANA System in SAP HANA Studio

Read here Steps to Download and Install SAP HANA Studio


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