Re: Cron management...
Date: Thu, 23 Apr 2015 16:08:52 -0600
Message-ID: <55396D74.3060509_at_gmail.com>
On 23/04/2015 3:08 PM, Mladen Gogala (Redacted sender mgogala_at_yahoo.com for DMARC) wrote:
> On 04/23/2015 10:27 AM, Jeremy Schneider wrote:
>>> >The "rman" executable is a client, similar to sqlplus,
>>> >which executes the internal functions, built into the Oracle
>>> executable
>>> >itself and delivers the data to the destination using the channels.
>> This is also exactly wrong. Also this is specifically the
>> misunderstanding that Hans was trying to correct.
>>
> Yes. And he expressed that disagreement by the sentence "We are in
> complete agreement". For the record, what is wrong with the paragraph?
>
I don't think there is a huge disagreement, but rather a simple lack of clarity.
"Executes Internal Functions" can sound like the RMAN executable itself does that. When I agreed with you, I relied on the "similar to sqlplus" in that SQLPlus does not do actual SQL or PL/SQL processing, but rather coordinates command interaction with the server process(es). In a similar fashion, the RMAN executable does not do the backup, but rather tells its server process what to do for the backup.
Again, from the docs at
http://docs.oracle.com/database/121/BRADV/rcmarchi.htm#BRADV105
"The RMAN client *directs database server sessions to perform all backup and recovery tasks*. What constitutes a session depends on the operating system. For example, on Linux, a server session corresponds to a server process, whereas on Windows it corresponds to a thread within the database service. The RMAN client itself does not perform backup, restore, or recovery operations.
An RMAN channel represents one stream of data to a device, and corresponds to one database server session. During a backup or restore operation, the channel reads data from the input device, processes it, and writes it to the output device. See "Basic Concepts of RMAN Performance Tuning" for a low-level description of how channels work."
No matter which way we slice it, since the 'Channel' reads blocks from the database and puts them into in-memory output buffers to be written to disk or transferred via MML to media (or vice versa for restore), MML itself needs to be on the same machine(s) as the server processes that read/write the data blocks.
/Hans
(By the way - "I'm glad we agree" != "We are in complete agreement" ...
subtly different.)
-- http://www.freelists.org/webpage/oracle-lReceived on Fri Apr 24 2015 - 00:08:52 CEST