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STRERROR()

Syntax

STRERROR( [ <expN> ] )

Description

The STRERROR() function returns a string describing the last operating system error message. If the optional error number is specified then the related operating system error message will be returned.

Example

mqdes=mqcreate("/myqueue", 2)
 if (mqdes < 0)
     messagebox(strerror()+",errno="+alltrim(str(error())))
    return
 endif
 rc = mqsend(mqdes, "Test message")
 if (rc < 0)
     messagebox(strerror()+",errno="+alltrim(str(error())))
    return
 endif
 mqclose(mqdes)

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Recital is a dynamic programming language with an integrated high performance database particularly well suited for the development and deployment of high transaction throughput applications.  Recital 10 further enhances Recital with extensive features and functionality to facilitate its use in fault tolerant high availability systems. Much of the development of Recital 10 was concentrated on performance optimizations and cluster aware functionality to provide an application platform that can be scaled as needed without any application changes. 

Key features of Recital 10 include:

  • Cluster aware database engine that works transparently with drbd, heartbeat, glusterfs and samba
  • High degree of fault tolerance with self healing indexes
  • Massive performance improvements 
  • Extensive internals overall and modernization with superior object-oriented capabilities
  • Chronological data versioning with database timelines
  • SmartQuery caching
  • Database Administration Tools
  • Code and Data Profiling
  • Better integration with unix/linux command shell
  • Incorporates a range of new built-in functions compatible with those in the PHP core libraries
  • Built-in support for outputting data in HTML, XML, and JSON format
  • Seamless SQL command integration into the Recital scripting language
  • Much improved Microsoft FoxPRO language compatibility
  • Numerous extensions and improvements (see below for details)
  • Very large file support (2^63)
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Recital 10 introduced the ECHO command. This command operates in the same way as the PHP ECHO command. It does not append a newline to the output but rather operates in the same way as the existing ?? command in Recital. The string being output can contain C-style string escapes \n \t or \r (newline, tab and carriage return respectively) e.g.
echo "Hello world\n"
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When using Recital Web you can maintain the exact state of each work area between pages like this.

On exit of an .rsp page.

SAVE DATASESSION TO m_state 
_SESSION["state"] = m_state

On entry to an .rsp page.

IF type( _session["state"] ) != "U" 
    m_state = _session["state"]
    RESTORE DATASESSION FROM m_state
ENDIF
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It would appear that gigabit LAN is not! In fact it often runs at the same speed as 100Mbps LAN. Let's look at why exactly.

After configuring your network you can use the ifconfig command to see what speeds the LAN is connected. Even though 1000Mbps is reported by the card, the reality is that the overall throughtput may well be ~100Mpbs. You can try copying a large file using scp to demonstrate this.

As it turns out, in order to use a gigabit LAN you need to use CAT6 cables. CAT5 and CAT5E are not good enough. End result, the ethernet cards throttle back the speed to reduce dropped packets and errors.

You can find a good article here titled Squeeze Your Gigabit NIC for Top Performance. After tuning up the TCP parameters i found that it made no dfifference. The principal reasons behind low gigabit ethernet performance can be summed up as follows.

  1. Need to use CAT6 cables
  2. Slow Disk speed
  3. Limitations of the PCI bus which the gigabit ethernet cards use

You can get an idea about the disk speed using the hdparm command:

Display the disk partitions and choose the main linux partition which has the / filesystem.

# fdisk -l


Then get disk cache and disk read statistics:

# hdparm -Tt /dev/sda0


On my desktop system the sata disk perfomance is a limiting factor. These were the results:

/dev/sda1:
Timing cached reads:   9984 MB in  2.00 seconds = 4996.41 MB/sec
Timing buffered disk reads:   84 MB in  3.13 seconds =  58.49 MB/sec

Well, that equates to a raw disk read speed of 58.49 * 8 = 467Mbps which is half the speed of a gigabit LAN.

So.. NAS storage with lots of memory looks to be the way to go... If you use the right cables!


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The first step is to create an Apple Disk Image File (DMG) distribution in a GUI tool, I used DMG Packager.
Then create a directory that will contain all the files that you want included in the DMG file. The best way to do this is to mount the DMG file you created and copy the files into this directory. Then move the .app file created by BitRock into this directory.
Then run the hdiutil utility to create a DMG file
$hdiutil create /tmp/tmp.dmg -ov -volname "RecitalInstall" -fs HFS+ -srcfolder "/tmp/macosxdist/" 
Finally call hdutil to convert the writable, to a compressed (and such not writable) DMG
$hdiutil convert /tmp/tmp.dmg -format UDZO -o RecitalInstall.dmg
So now each time before you build a new distribution with the above commands, just move the new .app file into the directory containing the files to be added to the DMG file.
I've already added this to the makefile so after BitRock creates the .app file the hdiutil command is called to automatically generate the new DMG file.
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If when your attempt to create device meta-data fails this is drbd preventing you from corrupting a file system present on the target partition.

$ drbdadm create-md drbd0

v08 Magic number not found
md_offset 30005817344
al_offset 30005784576
bm_offset 30004867072

Found ext2 filesystem which uses 190804004 kB
current configuration leaves usable 29301628 kB

Device size would be truncated, which
would corrupt data and result in
'access beyond end of device' errors.
You need to either
* use external meta data (recommended)
* shrink that filesystem first
* zero out the device (destroy the filesystem)
Operation refused.

Command 'drbdmeta /dev/drbd0 v08 /dev/sda4 internal create-md' terminated with exit code 40
drbdadm aborting

Once you have confirmed that the file system present on the target partition is no longer required at the prompt type the following:

Replace /dev/sdaX with the block device you are targeting.

dd if=/dev/zero of=/dev/sdaX bs=1M count=128

Once this has completed the drbdadm create-md drbd0 command will complete with a "success."

$ drbdadm create-md drbd0
v08 Magic number not found
v07 Magic number not found
v07 Magic number not found
v08 Magic number not found
Writing meta data...
initialising activity log
NOT initialized bitmap
New drbd meta data block successfully created.
success
$

 

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This guide will assist you in setting up an rsnapshot backup server on your network. rsnapshot uses rsync via ssh to perform unattended backups of multiple systems in your network. The guide can be found on the centos website here.

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A quick tip for optimizing TCP performance on linux.

edit /etc/sysctl.conf add the lines:

If using gigabit ethernet:

net.ipv4.tcp_mem= 98304 131072 196608
net.ipv4.tcp_window_scaling=1
net.core.wmem_default = 65536
net.core.rmem_default = 65536
net.core.wmem_max=8388608

To reload these use:

# sysctl -p

If using infiniband:

net.ipv4.tcp_window_scaling=1
net.ipv4.tcp_timestamps=0
net.ipv4.tcp_sack=0
net.ipv4.tcp_rmem=10000000 10000000 10000000
net.ipv4.tcp_wmem=10000000 10000000 10000000
net.ipv4.tcp_mem=10000000 10000000 10000000
net.core.rmem_max=524287
net.core.wmem_max=524287
net.core.rmem_default=524287
net.core.wmem_default=524287
net.core.optmem_max=524287
net.core.netdev_max_backlog=300000

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