Hello,

Some information I've got from TSM support that can be good to know about

DIRMC don't need to be configured to back up directories to a (separate) 
disk storage pool

DIRMC specifies the management class (MC) for directories to bind to. 
If not specified, by default, the MC class in the active policy set of the 
policy domain with the longest retention period will be used for 
directories. 
If more than one MC with the same long retention period is configured, the 
highest in alphabetical order will be used.
It is recommended that you select a MC for individual directories that 
retains directories at least as long as it retains the files associated 
with them.

Restore order with TSM versions before Version 3 1997, two steps
1. Restore directories
2. Restore files
DIRMC had a big impact on restore performance
Best practice - >
Advantageous to have directory information cached on disk to prevent from
Unwanted tape mounts
Unwanted tape locates

Restore order with TSM versions after TSM Versions 3 and newer
Restore order changed:
Single step restore, files and directories
Two step directory processing:
1. Create directories with default attributes. Directory information 
coming from the stored file object
2. Correct attributes and ACLs once data is read from tape

DIRMC effects on transaction processing
Transactions are used to create server aggregates, groups of logical files 
an aggregate represents 
1 server physical file
Multiple client logical files
Transaction options
TXNGROUPMAX (server, default 256)
TXNBYTELIMIT (client, default 25600)
Transactions allow improved server performance during server internal data 
movement operatons, e.g. Migration, backup storage pool etc.

What happens during backup?
If the client detects a change in the destination for the object to back 
up:
End the current transaction independent of
TXNGROUPMAX
TXNBYTELIMIT
Begin a new transaction
Back up the object with reset transaction boundaries. In most cases the 
next object will be a file object again, so the current directory 
transaction will be ended and a new transaction will be started for the 
file objects.
The directory will be send to the server as a single object within a 
transaction.This results in less objects being aggregated than expected

Although the DIRMC is no longer required to optimize the directory restore 
stage it is still usefull:
By default, directories are bound to the management class in the active 
policy set of your policy domain with the longest retention period and 
then highest in alphabetical order, which could point to a storage pool on 
tape 
unexpected mounts during restore
unexpected time to locate the directory objects on tape
To take maximum advantage of transaction boundaries and optimize server 
internal data movement operations, bind the directories to a MC with the 
same destination as the MC of the file objects, e.g. bind the directories 
to the same MC as the file objects (best practice).
It is not required or recommended to have the DIRMC bind to a MC with a 
separate disk storage pool destination
____________________________________________

Kind Regards
Mikael Lindström

IBM Svenska AB SE-164 92 Stockholm, Sweden
Visiting address: Oddegatan 5, Kista
Mob: +46 70793 5096
E-mail: mikael.lindstrom AT se.ibm DOT com

Prepared by IBM Attorney - IBM Confidential (Unless indicated otherwise)  



Christian Svensson <Christian.Svensson AT CRISTIE DOT SE> 
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
2009-01-22 11:21
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[ADSM-L] SV: DIRMC






Hi,
DIRMC option could help you a lot depend on how you configure it.
Make sure you configure DIRMC to save it's data on Disk only.

Best Regards
Christian Svensson

Cell: +46-70-325 1577
E-mail: Christian.Svensson AT cristie DOT se
Skype: cristie.christian.svensson
________________________________________
Från: ADSM: Dist Stor Manager [ADSM-L AT VM.MARIST DOT EDU] f&#246;r ashish 
sharma [ashishsharma44 AT GMAIL DOT COM]
Skickat: den 22 januari 2009 06:31
Till: ADSM-L AT VM.MARIST DOT EDU
Ämne: DIRMC

Hello,

How could DIRMC option on server side improve the restore time.Any idea?

--
Best Regards
Ashish Sharma
ST Microelectronics Ltd.
919717003853



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