An index in the write-ahead log showing the last successful replication.
aka: Commit Index
Problem
The Write-Ahead Log pattern is used to recover state after a server crashes and restarts. But a write-ahead log is not enough to provide availability in case of server failure. If a single server fails, then clients won't be able to function until the server restarts. To get a more available system, we can replicate the log on multiple servers. Using Leader and Followers the leader replicates all its log entries to a Majority Quorum of followers. Now, should the leader fail, a new leader can be elected, and clients can mostly continue to work with the cluster as before. But there are still a couple things that can go wrong:
- The leader can fail before sending its log entries to any followers.
- The leader can fail after sending log entries to some followers, but before sending it to the majority of followers.
In these error scenarios, some followers can be missing entries in their logs, and some followers can have more entries than others. So it becomes important for each follower to know what part of the log is safe to be made available to the clients.
Solution
The high-water mark is an index into the log file that records the last log entry known to have successfully replicated to a Majority Quorum of followers. The leader also passes on the high-water mark to its followers during its replication. All servers in the cluster should only transmit to clients the data that reflects updates below the high-water mark.
for more details go to Chapter 10 of the online ebook at oreilly.com
FAQs
Mud lines on hard surfaces tend to leave better-quality high-water marks, especially when deposited by tranquil water. Excellent mud lines can form on stone, metal, plastic, and glass surfaces. Mud lines on structures may last for many weeks if undisturbed or may be washed away quickly during cleanup efforts.
How to resolve a high water mark in Oracle? ›
TRUNCATE will reset the HWM of a table back to 'zero' and will truncate the associated indexes on the table as well. If you plan on deleting every row in a table, TRUNCATE¿if it can be used¿would be the method of choice for this reason.
What is considered a high water mark? ›
Federal regulations define the ordinary high water mark (OHWM) as “that line on the shore established by the fluctuations of water and indicated by physical characteristics such as a clear, natural line impressed on the bank, shelving, changes in the character of soil, destruction of terrestrial vegetation, the ...
What is the high watermark calculation? ›
High-water mark indexing is used in investment management to calculate the performance fees charged by hedge funds or other investment funds. It is designed to ensure that the fund manager is only rewarded for generating positive returns for investors.
How do you find the ordinary high-water mark? ›
Well established, mature vegetation is an excellent primary indicator of OHWM. Locations where historic stabilization has been placed is another key indicator. Bank erosion and undercutting, exposed root systems, changes in bank vegetation, and water staining on rocks are common indicators.
What is a high watermark value? ›
High-water mark is the highest level of value reached by an investment account or portfolio. It is often used as a threshold to determine whether a fund manager can gain a performance fee.
What is an ordinary high-water mark? ›
“The term ordinary high water mark means that. line on the shore established by the fluctuations. of water and indicated by physical. characteristics such as clear, natural line. impressed on the bank, shelving, changes in.
What is the 2 20 rule? ›
The 2 and 20 is a hedge fund compensation structure consisting of a management fee and a performance fee. 2% represents a management fee which is applied to the total assets under management. A 20% performance fee is charged on the profits that the hedge fund generates, beyond a specified minimum threshold.
What is high-water mark look back period? ›
High Water Marking lets you:
Specify a look-back period (in quarters or years, based on the period selection in the Percent of P&L fee schedule). High Water Marking keeps track of cumulative losses per billing period within the specified look-back period.
Is a high-water mark calculated before or after fees? ›
Will the performance fee operate with a high water mark? The performance fee calculation is subject to a high water mark which must be exceeded before a performance fee is accrued. This is designed to ensure that a performance fee is not charged until any previous losses have been recovered.
A high-water mark is the highest value an investment fund or account has ever reached. A hurdle rate is the minimum profit or returns a hedge fund must earn before charging an incentive fee.
What is the high watermark approach? ›
The purpose is to protect investors from paying a fee for poor performance, and from paying a fee repeatedly every time the fund earns a profit. With a high-water mark, the investor pays a fee that only covers the amount the fund earned between the point of entry and its highest level.
How do you determine the mean high water line? ›
To determine the elevation of Mean High Tide Line on the shore one should use either the published Mean High Water elevation from a National Oceanic and Atmospheric Agency published tide station closest to the project or a linear interpolation between two adjacent tide stations, depending on the most appropriate ...
What is the high water mark value? ›
A high-water mark is the highest level in value an investment account or fund has reached. A high-water mark is often used as a demarcation point in determining performance fees that an investor must pay.
How can a rider determine the ordinary high water mark (OHWM)? ›
Knowing that the amplitude is a measure of the wave's strength or extent of displacement from the still water mark, a rider, in this case, can determine the Ordinary High Water Mark by recognizing that it typically corresponds to the point where the presence and action of water is so common and long-lasting in ordinary ...
What is the difference between high water mark and low water mark? ›
A quick definition of high-water mark:
It can also refer to the line that a river leaves on the soil when it covers it for a long time. The low-water mark is the opposite, showing the lowest point that water reaches during low tide in the sea or a river.
