Ext3 commits writes to disk within approximately 5 seconds - Ext4 can take from 40-150 seconds. In addition, if a system is using Ext3 and crashes before the commit takes place you will still have the previous contents of a file where under Ext4 the file will be empty. Theodore Tso feels that this is a failure at the application level and that the file system is behaving as designed and as specified by the POSIX spec (which apparently does not specify what is supposed to happen when a system is not shut down cleanly). His solution to the issue is to suggest proper use of fsync() and lists various scenarios/examples in post 54 of the bug report (linked above). In addition he wrote a patch that recognize the rename() situation mentioned in his post 54 yet retains the normal Ext4 behaviors and performance in the majority of cases. Also a more "proper" solution has been provided which allows the behavior of Ext3 to be retained under Ext4 by mounting it with alloc_on_commit.
A somewhat related topic is the use of on-board caching by hard drives. This behavior can be modified on most drives by using hdparm.
Recital is a rich and versatile product with many ways to do the same thing. Developers usually write code in the way that they are accustomed to without paying much attention to how this will perform in a multi-user environment with large amounts of users and transactions. The best way to optimize Recital applications is to use the built-in tuning capabilities introduced in Recital 10.
Binary distributions for Unison can be found here.
The user manual can be found here.
echo "Hello world\n"
The best way to learn Recital is to build some applications. The developers of Recital have written a book "Recital Essentials" which you can read here.
USE accounts INDEX on account_no TAG outstanding FOR balance > 0 EXPLAIN SELECT * FROM accounts WHERE balance > 0 Optimized using for condition on tag 'OUTSTANDING'
Here's how to set up field validation based on dynamic values from another table.
Using the products.dbf table from the southwind sample database, validation can be added to the categoryid field to ensure it matches an existing categoryid from the categories.dbf table.
open database southwindThe rlookup() function checks whether an expression exists in the index (master or specified) of the specified table . An attempt to update categoryid with a value not in the list will give an error: Validation on field 'CATEGORYID' failed.
alter table products add constraint;
(categoryid set check rlookup(products.categoryid,categories))
If you have access to the Recital Workbench, you can use the modify structure worksurface to add and alter your dictionary entries, including a customized error message if required.
The Openfiler NAS/SAN Appliance (NSA) is a Storage Management Operating System / NAS Appliance distribution. It is powered by the Linux 2.6 kernel and Open Source applications such as Apache, Samba, LVM2, ext3, Linux NFS and iSCSI Enterprise Target. Openfiler combines these ubiquitous technologies into a small, easy to manage solution fronted by a powerful web-based management interface. Openfiler allows you to build a Network Attached Storage (NAS) and/or Storage Area Network (SAN) appliance, using industry-standard hardware, in less than 10 minutes of installation time.
Building upon the popularity of server virtualization technologies such as VMware, Virtual Iron, and Xen, Openfiler can also be deployed as a virtual machine instance or on a bare metal machine.
This deployment flexibility of Openfiler ensures that storage administrators are able to make the best use of system performance and storage capacity resources when allocating and managing networked storage in a multi-platform environment.
Openfiler is ideally suited for use with High Availability Recital applications as it incorporates:
- Heartbeat cluster manager
- drbd disk replication
- CIFS
- NFS
- Software and hardware RAID
- FTP
- rsync
- HTTP/DAV
- iSCSI
- LVM2
- Multiple NIC bonding for High Availability
- Powerful web-based GUI
Recital is a dynamic programming language with an embedded high performance database engine particularly well suited for the development and deployment of high transaction throughput applications.
The Recital database engine is not a standalone process with which the application program communicates. Instead, the Recital database is an integral part of any applications developed in Recital.
Recital implements most of the SQL-99 standard for SQL, but also provides lower level navigational data access for performing high transaction throughput. It is the choice of the application developer whether to use SQL, navigational data access, or a combination of both depending upon the type of application being developed.
The Recital database engine, although operating as an embedded database in the user process, multiple users and other background processes may access the same data concurrently. Read accesses are satisfied in parallel. Recital uses automatic record level locking when performing database updates. This provides for a high degree of database concurrency and superior application performance and differentiates the Recital database from other embeddable databases such as sqlite that locks the entire database file during writing.
Key features of the Recital scripting language include:
- High performance database application scripting language
- Modern object-oriented language features
- Easy to learn, easy to use
- Fast, just-in-time compiled
- Loosely-typed
- Garbage collected
- Static arrays, Associative arrays and objects
- Develop desktop or web applications
- Cross-platform support
- Extensive built-in functions
- Superb built-in SQL command integration
- Navigational data access for the most demanding applications
- Scripting language is upward compatible with FoxPRO
Key features of the Recital database include:
- A broad subset of ANSI SQL 99, as well as extensions
- Cross-platform support
- Stored procedures
- Triggers
- Cursors
- Updatable Views
- System Tables
- Query caching
- Sub-SELECTs (i.e. nested SELECTs)
- Embedded database library
- Fault tolerant clustering support
- Chronological data versioning with database timelines
- Optional DES3 encrypted data
- Hot backup
- Client drivers for ODBC, JDBC and .NET
Here is a simple shell script to copy your ssh authorization key to a remote machine so that you can run ssh and scp without having to repeatedly login.
#!/bin/sh
# save in file ssh_copykeyto.sh then chmod +x ssh_copykeyto.sh
KEY="$HOME/.ssh/id_rsa.pub"
if [ ! -f ~/.ssh/id_rsa.pub ];then
echo "private key not found at $KEY"
echo "create it with "ssh-keygen -t rsa" before running this script
exit
fi
if [ -z $1 ];then
echo "Bad args: specify user@host as the first argument to this script"
exit
fi
echo "Copying ssh authorization key to $1... "
KEYCODE=`cat $KEY`
ssh -q $1 "mkdir ~/.ssh 2>/dev/null; chmod 700 ~/.ssh; echo "$KEYCODE" >> ~/.ssh/authorized_keys; \ chmod 644 ~/.ssh/authorized_keys"
echo "done!"