RMAN restore expertise

[netbackup_rooki]

Hi

i am looking to increase restore times for RMAN backups from Tape and don't mind increasing backup times. I have done some testing by playing around with different Mulitiplex settings on netbackup side but restore time doesn't change. RMAN is configured for 4 channel backup and I have tried the backup and restore with files per set and set size RMAN parameters. I am looking for you expert ideas..advice.

i will also test to disk and i am sure the time can be reduced but currently my options are only tape...Thanks in advance.

[Taqadus_Rehman]

 I am not very good with RMAN but still few tips

- use BACKUP ... VALIDATE to derermine whether tape streaming or disk I/O is the bottleneck.
- use multiplexing to improve tape streaming with disk bottleneck.

there are different multiplexing level

- For Read

Level <= 4 -------- 1MB Buffers are allocated so that the total bufer size for all the input file s is 16MB

4< Level <=8 ----- 512MB Buffers are allocated so that the total bufer size for all the input file s is less then 16MB

Level > 8 ----------- RMAN Allocates four 128 KB disk buffers per channel for each file, so that total size is 512KB per channel for each file.

- For Write

each channel allocates for output buffers of 1MB each.

[Nicolai]

Have you configured NUMBER_DATA_BUFFERS_RESTORE /  NUMBER_DATA_BUFFERS_RESTORE_DISK on the media server. If you running default, this may very well be you're  bottleneck.

Regards

Nicolai

[netbackup_rooki]

Buffers and Multiplexing is in place. As far as the multiplexing. although i have it configured but it really impacts your restore because it will only read a single stream at a time when restoring and the other streams will show active but data is not being read from them. I believe this is because of the nature of Tape drives.

[Nicolai]

Have you set MPX_RESTORE_DELAY ? at least in theory that should make all 4 stream restore at the same time.

But I often see the same issue with only half of the streams going active (SAP cloning).

Nicolai

[netbackup_rooki]

my understanding about tape backup is that you can write mulitple but read only one, since it can only read one tape mark at a time and thats why the others are showing begin reading but really aren't doing any data transfer. As far the MPX_RESTORE_DELAY, it is set to 30 sec (i believe this by default)