MySQL Forums
Forum List  »  NDB clusters

Re: FragLog Files
Posted by: Mikael Ronström
Date: March 17, 2017 02:31AM

No files can be removed.
Here is an explanation of them:

1) FragLog files (REDO log files)
The total size of the REDO log files are:
NoOfFragmentLogParts * NoOfFragmentLogFiles * FragmentLogFileSize

NoOfFragmentLogParts defaults to 4 and cannot be set lower than 4.
NoOfFragmentLogParts needs to be increased to match the number of
LDM threads if the number of LDM threads is larger than 4, otherwise
tables are not evenly partitioned on the LDM threads.

So in your case this equation becomes:
4 * 40 * 128M = 20G

The REDO log needs to big enough to handle REDO logs generated
over the time of 2 LCPs. At the beginning of the 2nd LCP we cut
the REDO log tail of the old LCP, so at this point we have REDO
logs for 2 LCPs plus the time between end of LCP and start of
LCP (very short if REDO log is close to full).

If tail meet head in REDO log you will get error 410 indicating
that you have run out of REDO log space if any updating transactions
are performed, reads are still ok.

This is a temporary condition that will last until the REDO log is
cut such that tail is moved forward again.
For most installations the worst case for the REDO log is when
loading data.

2) LCP files
These are the local checkpoint files. We keep 2 LCPs around.
So this means your data size is likely to be around 8G. So
this is not possible to change.

One way to decrease the size of LCP files is to use compression
of the LCPs. There is a config variable for this. This will use
zlib to compress the LCP files. Usually delivers at least a
2x compression.

REDO log files cannot be compressed.

Options: ReplyQuote


Subject
Views
Written By
Posted
171
March 16, 2017 09:41AM
114
March 16, 2017 10:33AM
72
March 16, 2017 10:45AM
Re: FragLog Files
100
March 17, 2017 02:31AM


Sorry, only registered users may post in this forum.

Content reproduced on this site is the property of the respective copyright holders. It is not reviewed in advance by Oracle and does not necessarily represent the opinion of Oracle or any other party.