Each Recital table can have one or more data dictionaries to provide a central repository for constraints and other metadata. 

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 southwind
alter table products add constraint;
 (categoryid set check rlookup(products.categoryid,categories))

The 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.

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.

Many motherboards nowadays have integrated gigabit ethernet that use the Realtek NIC chipset.

The Realtek r8168B network card does not work out of the box in Redhat/Centos 5.3: instead of loading the r8168 driver, modprobe loads the r8169 driver, which is broken as can be seen with ifconfig which shows large amounts of dropped packets. A solution is to download the r8168 driver from the Realtek website and install it using the following steps:

Check whether the built-in driver, r8169.ko (or r8169.o for kernel 2.4.x), is installed.

# lsmod | grep r8169

If it is installed remove it.

# rmmod r8169

Download the R8168B linux driver from here into /root.

Unpack the tarball :

# cd /root
# tar vjxf r8168-8.012.00.tar.bz2

Change to the directory:

# cd r8168-8.012.00

If you are running the target kernel, then you should be able to do :

# make clean modules   
# make install
# depmod -a
# insmod ./src/r8168.ko (or r8168.o in linux kernel 2.4.x)

make sure modprobe knows not to use r8169, and that depmod doesn’t find the r8169 module.

# echo "blacklist r8169" >> /etc/modprobe.d/blacklist
# mv /lib/modules/`uname -r`/kernel/drivers/net/r8169.ko   \
        /lib/modules/`uname -r`/kernel/drivers/net/r8169.ko.bak

You can check whether the driver is loaded by using the following commands.

# lsmod | grep r8168
# ifconfig -a

If there is a device name, ethX, shown on the monitor, the linux driver is loaded. Then, you can use the following command to activate it.

# ifconfig ethX up

After this you should not see any more dropped packets reported.

When stress testing our loadbalancer, i was unable to get more than 20 reliable ssh connections. The following error would be reported.

ssh_exchange_identification: Connection closed by remote host

The resolution for this is quite simple.

Edit the /etc/ssh/sshd_config file and increase the MaxStartups. On my server i set this to 200.

Edit /etc/sysctrl.conf and add the following line:

net.core.netdev_max_backlog = 3000

Then apply this change:

# sysctl -p