Timesten - Database Installation and configuration on Linux

> Database > (TimesTen|TT) (In-Memory Database|IMDB)

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1 - About

On UNIX/Linux systems before installing application, you must in general configure the following:

In addition for timesten, you need to perform the following:

  • Ensure you have the latest operating system patches.
  • Configure your file system to allow large files.
  • Configure your Java environment.
  • Configure your Client/Server environment.
  • Configure network settings for replication.
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3 - Prerequisites

Before installing TimesTen, ensure that, the user installing TimesTen is a member of the administrator's group and has read and write permissions on the /etc/TimesTen directory

4 - Semaphores

TimesTen consumes:

Semaphore Per Active Database Plus Example
SEMMNI one one additional per TT instance
(where Client/Server communication is done through shared memory.)
SEMMSL 155 one for each connection With a Connections attribute value of 100, TT requires a minimum of 255.

It is best to set the SEMMSL parameter to a higher value, for example for Linux x8664 to support 2000 connections you should set the following line to the /etc/sysctl.conf

kernel.sem = 2200   6400   200    25
kernel.sem = SEMMSL SEMMNS SEMOPM SEMMNI

4.1 - IPC Client/Server

On Red Hat Linux systems, to enable more than 6 ShmIpc Client/Server connections, add the following line to the /etc/sysctl.conf file:

kernel.sem = 270 32000 100 128

5 - Other Client/Server settings

The maximum number of concurrent IPC connections to a TimesTen Server allowed by TimesTen is 9,999.

However, system limits can take precedence on the number of connections to a single DSN. Client/Server users can increase the file descriptor limit to support a large number of connections and processes.

For example, on Solaris, you may change the file descriptor limit to have a maximum of 1024 simultaneous server connections by adding the following line to /etc/system:

set rlim_fd_max = 1080

In this case, 1080 is greater than the number of anticipated client/server connections and allows for a few extra connections.

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6 - Operating Systeem certification

For Linux, TimesTen has been tested with:

  • Asianux 2.0 and 3.0,
  • Red Hat Enterprise Linux 4 and 5,
  • the MontaVista Linux Carrier Grade Edition Release 4.0 and 5.0
  • and SuSE LINUX Enterprise Server 10 minimal configurations.

TimesTen does not support SELinux. When installing Linux for use with TimesTen, ensure that the SELinux option is disabled.

7 - Shared memory

To increase the shared memory size to 2048 MB, log in as root and edit the /etc/sysctl.conf file by adding the line:

kernel.shmmax=2147483648

If your configuration is greater than 8 GB, you should also increase the value of the shmall parameter. The value is in KB and should be equal to

ceil(SHMMAX/{PAGE SIZE})

Page size is generally 4K on x86 systems and 16K on Itanium. For example, for a 64 GB database on Itanium, you should specify the following parameters values:

kernel.shmmax=68719476736
kernel.shmall=4194304

To increase the shared memory size without rebooting, use:

% /sbin/sysctl -w kernel.shmmax=2147483648

If you have your kernel configured with the /proc file system and it is mounted, then the current maximum shared memory segment size (in bytes) can be viewed by the following command:

% cat /proc/sys/kernel/shmmax

You can also change this value by the following command:

% echo 2147483648 > /proc/sys/kernel/shmmax

This command has the same effect as the sysctl command.

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8 - Limits on number of open files

Each process connected to a TimesTen database keeps at least one operating-system file descriptor open from the time of the first connection until the process terminates.

Additional file descriptors may be opened for each database connection:

  • Connections to databases that have logging to disk enabled require an additional two file descriptors for the duration of the connection.
  • An additional file descriptor is needed for the duration of database checkpoints issued by the process.
  • Additional file descriptors may be opened during transaction commit or rollback operations.

For multithreaded applications that maintain many concurrent TimesTen database connections, the default number of open files permitted to each process by the operating system may be too low.

  • On Solaris, the default limit is 256 open files and may be raised for a session with the ulimit command (limit for csh users). You can also set the per-process limit programmatically with setrlimit.
  • On AIX, the limit is 2,048 open files, so you are not likely to encounter problems.
  • On Linux, the default limit is 1,024 open files, so you are not likely to encounter problems.
  • On Windows, the default limit is at least 2,000 open files, so you are not likely to encounter problems.

Most of the open file descriptors are used for reading and writing database recovery log files. If a process fails to open a log file, the database is marked as requiring recovery and all current connections to the database are terminated.

9 - Documentation / Reference