These topics provide an overview of setting up and configuring remote standalone (RSS) secondary servers in a high availability environment.

1 RSS Technology

RSS ( Remote Standalone Secondary server) is very similar to HDR, especially in setup and behavior. It is a full copy of an instance, and it can help with load balancing.

When comparing the two, RSS is different from HDR in several distinct ways. For example:

  1. The communication protocol is fully duplexed to allow better communication over slower lines.
  2. There is no synchronous mode of running RSS servers (including checkpoints).
  3. An RSS server cannot be promoted to a Primary.
  4. There can be any number of RSS servers.
  5. Index Page Logging must be enabled.

However, RSS and HDR technologies can work well together. Even though there can only be one HDR Secondary at a time. it is quite easy to convert an RSS server to a HDR Secondary, and back again.

Prior to RSS, when a log buffer was flushed to disk, a copy of that page was sent to the HDR log buffer and the ER buffer cache. Now, with RSS, the Primary server also checks to see if there are RSS servers. If so, then a copy of that buffer will be sent to the cache, which will be used to send the information to the RSS server. If the RSS Send thread is sleeping, then the thread will be awakened to send the information to the RSS server. This concept is represented in the following figure.

2 Requirements

Version of the database servers

The versions of the primary and secondary database servers must be the same.

Configuring dbspaces and chunks

The number of dbspaces, the number of chunks, their sizes, and the pathnames and their offsets must be identical on the primary and secondary servers.

Configuration Parameters

The ONCONFIG parameters shown below must have the same value on the two database servers:

  • ROOTNAME

  • ROOTOFFSET

  • ROOTPATH

  • ROOTSIZE

  • PHYSDBS

  • PHYSFILE

  • LTAPEDEV

  • LTAPEBLK

  • LTAPESIZE

  • TAPEBLK

  • TAPESIZE

  • STACKSIZE

3 Setting up RSS

RSS has a setup procedure that is similar to HDR. The following sections step through this process, where you just copy the chunks to another location. The process is simplified because there are no archiving algorithms included.


On the Primary (Machine pdemodb):

  1. Set LOG_INDEX_BUILDS and ENABLE_SNAPSHOT_COPY to 1 in the onconfig.
    Copy 
    # LOG_INDEX_BUILDS  - Enable (1) or disable (0) index page logging.
#                     Required for RSS. Optional for HDR and SDS.
LOG_INDEX_BUILDS      1
ENABLE_SNAPSHOT_COPY  1
  2. Add entries to the $INFORMIXSQLHOSTS and /etc/services files for network connections.
    • /etc/hosts file:
      Copy 
      192.168.56.101 pdemodb     #Primary server
192.168.56.111 rdemodb     #Secondary server
    • /etc/services file:
      Copy 
      sqlexec         9088/tcp                # IBM Informix SQL Interface
sqlexec         9088/udp                # IBM Informix SQL Interface
    • $ONCONFIG file:
      Copy 
      DBSERVERNAME    pdemodb
DBSERVERALIASES ol_pdemodb
HA_ALIAS        ol_pdemodb
    • $INFORMIXSQLHOSTS file:
      Copy 
      #Primary server
pdemodb         onipcshm        on_pdemodb      on_pdemodb
ol_pdemodb      onsoctcp        pdemodb         sqlexec

#Secondary server
ol_rdemodb      onsoctcp        rdemodb         sqlexec
  3. Modify the /etc/hosts.equiv or the .rhosts file for the informix user ID to enable trusted communication.
    • /etc/hosts.equiv file:
      Copy 
      #Secondary server
rdemodb
  4. Takes the database server to offline mode and removes shared memory.
    Copy 
    onmode -ky
  5. Copy the chunks files to the secondary machine.
    Copy 
    scp /INFORMIXDEV/* rdemodb:/INFORMIXDEV/
  6. Takes the database server to online mode.
    Copy 
    oninit
  7. Add instance ol_rdemodb as RS server
    Copy 
    onmode -d add RSS ol_rdemodb

On the Secondary (Machine rdemodb):

  1. Add entries to the $INFORMIXSQLHOSTS and /etc/services files for network connections.
    • /etc/hosts file:
      Copy 
      192.168.56.101 pdemodb     #Primary server
192.168.56.111 rdemodb     #Secondary server
    • /etc/services file:
      Copy 
      sqlexec         9088/tcp                # IBM Informix SQL Interface
sqlexec         9088/udp                # IBM Informix SQL Interface
    • $ONCONFIG file:
      Copy 
      DBSERVERNAME    rdemodb
DBSERVERALIASES ol_rdemodb
HA_ALIAS        ol_rdemodb
    • $INFORMIXSQLHOSTS file:
      Copy 
      #Secondary server
rdemodb         onipcshm        on_rdemodb      on_rdemodb
ol_rdemodb      onsoctcp        rdemodb         sqlexec

#Primary server
ol_pdemodb      onsoctcp        pdemodb         sqlexec
  2. Modify the /etc/hosts.equiv or the .rhosts file for the informix user ID to enable trusted communication.
    • /etc/hosts.equiv file:
      Copy 
      #Primary server
pdemodb

4 Verify that the RSS connection was successful

If the HDR connection is configured correctly, SQL statements can be executed from one server against the other. The following example can be done in both directions, from the primary to the secondary and from the secondary to the primary.

The following example is to do this from the primary server pdemodb.

Copy 
dbaccess

After choosing a database (any) and choosing the "New" menu, the following query is performed:

Copy 
Select * from NOMBRE_BD@DBSRVALIAS_MAQUINA_2:NOMBRE_TABLA;

For example:

Copy 
Select *  from sysmaster@ol_rdemodb:sysdatabases;

This must be done without errors. If an error occurs, it can be for one of the following reasons:

Copy 
908: Attempt to connect to database server (ol_pdemodb, conerr=-25555, oserr=0) failed.

In $INFORMIXDIR/etc/sqlhosts an entry is missing to connect to the server.

Copy 
956: Client host or user (informix@rdemodb) is not trusted by the server.

In /etc/hosts.equiv an entry is missing for trusted servers. This file indicates the aliases of cards defined in /etc/hosts for which access by that card is considered trusted.

5 Setting up RSS with ontape

The following sections show the steps for setting up RSS with ontape.


On the Primary (Machine pdemodb):

  1. Set LOG_INDEX_BUILDS to 1 in the onconfig.
    Copy 
    # LOG_INDEX_BUILDS  - Enable (1) or disable (0) index page logging.
#                     Required for RSS. Optional for HDR and SDS.
LOG_INDEX_BUILDS      1
  2. Add entries to the $INFORMIXSQLHOSTS and /etc/services files for network connections.
    • /etc/hosts file:
      Copy 
      192.168.56.101 pdemodb     #Primary server
192.168.56.111 rdemodb     #Secondary server
    • /etc/services file:
      Copy 
      sqlexec         9088/tcp                # IBM Informix SQL Interface
sqlexec         9088/udp                # IBM Informix SQL Interface
    • $ONCONFIG file:
      Copy 
      DBSERVERNAME    pdemodb
DBSERVERALIASES ol_pdemodb
HA_ALIAS        ol_pdemodb
    • $INFORMIXSQLHOSTS file:
      Copy 
      #Primary server
pdemodb         onipcshm        on_pdemodb      on_pdemodb
ol_pdemodb      onsoctcp        pdemodb         sqlexec

#Secondary server
ol_rdemodb      onsoctcp        rdemodb         sqlexec
  3. Modify the /etc/hosts.equiv or the .rhosts file for the informix user ID to enable trusted communication.
    • /etc/hosts.equiv file:
      Copy 
      #Secondary server
rdemodb

  4. Make sure the databases to be replicated are in logged mode.

    Copy 
    $ dbaccess sysmaster - -

Database selected.

> select * from sysdatabases where is_logging = 0;



No rows found.

  5. Run a backup level 0 and copy the generated file to the secondary machine.

    Copy 
    ontape -s -L 0
    Copy 
    scp /home/informix/IFMX-ONTAPES/pdemodb_0_L0 rdemodb:/home/informix/IFMX-ONTAPES/
  6. Add instance ol_rdemodb as RS server
    Copy 
    onmode -d add RSS ol_rdemodb

On the Secondary (Machine rdemodb):

  1. Add entries to the $INFORMIXSQLHOSTS and /etc/services files for network connections.
    • /etc/hosts file:
      Copy 
      192.168.56.101 pdemodb     #Primary server
192.168.56.111 rdemodb     #Secondary server
    • /etc/services file:
      Copy 
      sqlexec         9088/tcp                # IBM Informix SQL Interface
sqlexec         9088/udp                # IBM Informix SQL Interface
    • $ONCONFIG file:
      Copy 
      DBSERVERNAME    rdemodb
DBSERVERALIASES ol_rdemodb
HA_ALIAS        ol_rdemodb
    • $INFORMIXSQLHOSTS file:
      Copy 
      #Secondary server
rdemodb         onipcshm        on_rdemodb      on_rdemodb
ol_rdemodb      onsoctcp        rdemodb         sqlexec

#Primary server
ol_pdemodb      onsoctcp        pdemodb         sqlexec
  2. Modify the /etc/hosts.equiv or the .rhosts file for the informix user ID to enable trusted communication.
    • /etc/hosts.equiv file:
      Copy 
      #Primary server
pdemodb
  3. Make sure that all chunk paths are created, have the correct permissions, and ensure there is enough space on the disks for the data to reside.

  4. Run an physical restore.

    Copy 
    ontape -p -t /home/informix/IFMX-ONTAPES/pdemodb_0_L0
    . . .
Chunks
chk/dbs offset   size     free     bpages   flags pathname
1   1   0        150000   125174            PO--- /INFORMIXDEV/rootdbs
2   2   0        50000    24947             PO--E /INFORMIXDEV/d_plog
3   3   0        30250    197               PO--- /INFORMIXDEV/d_llog
4   4   0        50000    2522              POS-- /INFORMIXDEV/s_sbsys

. . .

Continue restore? (y/n) y
Do you want to back up the logs? (y/n) n
Restore a level 1 archive (y/n) n
  5. Sets an RS secondary server type
    Copy 
    onmode -d RSS ol_pdemodb

6 Changing modes (promote)

From RSS to HDR Secondary:

The RSS server can be converted into the HDR Secondary server by issuing following command:

Copy 
onmode -d secondary ol_pdemodb

From HDR Secondary to RSS:

Using following commands to change the HDR secondary server into an RSS server:

1. Register the RSS server name with the HDR primary server:

Copy 
onmode -d add RSS ol_rdemodb

2. On the HDR secondary, run the following command to change it to an RSS server:

Copy 
onmode -d RSS ol_pdemodb [optional password]

From RSS to Standard:

The RSS server should be converted to a standard server by issuing the following command:

Copy 
onmode -d standard

This step will make it a stand-alone server, and it will no longer be part of a cluster. To include RSS back in the high availability cluster, perform the following:

  • Restore the level-0 archive of the Primary server.
  • Add the RSS server information at the Primary.
  • Issue the onmode command to set up the RSS server.

7 Monitoring and troubleshooting RSS

There are three main ways to look at RSS:

  • The onstat command
  • The sysmaster database
  • Event alarms

7.1 onstat -g rss

The onstat -g rss command can be run on the Primary and any RSS server.

Example

Shows a sample run on a Primary.

Copy 
onstat -g rss
IBM Informix Dynamic Server Version 12.10.FC7ADE -- On-Line -- Up 04:04:58 -- 442536 Kbytes

Local server type: Primary
Index page logging status: Enabled
Index page logging was enabled at: 2017/08/01 10:19:00
Number of RSS servers: 1

RSS Server information:

RSS Srv      RSS Srv      Connection     Next LPG to send        Supports
name         status       status           (log id,page)         Proxy Writes
ol_rdemodb   Active       Connected             971,1877         N
Example

Shows a sample run on an RSS server.

Copy 
onstat -g rss
IBM Informix Dynamic Server Version 12.10.FC7ADE -- Read-Only (RSS) -- Up 00:21:55 -- 442536 Kbytes

Local server type: RSS
Server Status : Active
Source server name: ol_pdemodb
Connection status: Connected
Last log page received(log id,page): 971,1874

7.2 onstat -g rss verbose

It is possible to get even more information from onstat with the onstat -g rss verbose option.

Example

Shows a sample run on a Primary.

Copy 
onstat -g rss verbose
IBM Informix Dynamic Server Version 12.10.FC7ADE -- On-Line -- Up 04:13:01 -- 442536 Kbytes

Local server type: Primary
Index page logging status: Enabled
Index page logging was enabled at: 2017/08/01 10:19:00
Number of RSS servers: 1

RSS Server information:

RSS Server control block: 0x46c23170
RSS server name: ol_rdemodb
RSS server status: Active
RSS connection status: Connected
RSS flow control:384/352
Log transmission status: Active
Next log page to send(log id,page): 971,1877
Last log page acked(log id,page): 971,1876
Last log page applied(log id,page): 971,1876
Time of Last Acknowledgement: 2017-08-24.08:24:39
Pending Log Pages to be ACKed: 0
Approximate Log Page Backlog:0
Sequence number of next buffer to send: 66
Sequence number of last buffer acked: 65
Supports Proxy Writes: N

The verbose output will print this detailed information for all RSS server. As an alternative, use the onstat -g rss <name rss server> command to get detailed information for just one rss server.

Example

Shows a sample run of this command asking for more details on a single RSS server.

Copy 
onstat -g rss ol_rdemodb
IBM Informix Dynamic Server Version 12.10.FC7ADE -- On-Line -- Up 04:27:42 -- 442536 Kbytes

RSS Server control block: 0x46c23170
RSS server name: ol_rdemodb
RSS server status: Active
RSS connection status: Connected
RSS flow control:384/352
Log transmission status: Active
Next log page to send(log id,page): 971,2407
Last log page acked(log id,page): 971,2406
Last log page applied(log id,page): 971,2406
Time of Last Acknowledgement: 2017-08-24.08:39:40
Pending Log Pages to be ACKed: 0
Approximate Log Page Backlog:0
Sequence number of next buffer to send: 144
Sequence number of last buffer acked: 143
Supports Proxy Writes: N

Log Pages Snooped:
RSS Srv         From      From      Tossed
name            Cache     Disk     (LBC full)

ol_rdemodb         539        1868      0

7.3 onstat -g smx

The onstat -g smx command prints server multiplexer group information for servers using SMX. For each server it will show such information as:

  • The INFORMIXSERVER name
  • The address in shared memory of the SMX pipe
  • The encryption status
  • The number of bytes sent and received
  • The number of buffers sent and received
  • The number of write and read calls
  • The number of retries
Example

Shows a sample run of this command.

Copy 
onstat -g smx
IBM Informix Dynamic Server Version 12.10.FC7ADE -- On-Line -- Up 05:05:35 -- 442536 Kbytes

SMX connection statistics:
SMX control block: 0x45b22d28

  Peer server name: ol_rdemodb
  SMX connection address: 0x45b24328
  Encryption status: Disabled
  Total bytes sent: 5068236
  Total bytes received: 134716
  Total buffers sent: 2439
  Total buffers received: 4737
  Total write calls: 1716
  Total read calls: 4737
  Total retries for write call: 443
  Data compression level: 0
  Data sent: compressed 5068236 bytes by  0%
  Data received: compressed 134716 bytes by  0%

7.4 onstat -g smx ses

The onstat -g smx ses command will first print out the address in shared memory for the SMX control block. Then it will print a line for every server with the following information:

  • The INFORMIXSERVER.
  • The address in shared memory of the SMX session.
  • The type of connection. For RSS servers, this will typically say "RSS Send."
  • The number of reads and writes.
Example

Shows a sample run of this command.

Copy 
onstat -g smx ses
IBM Informix Dynamic Server Version 12.10.FC7ADE -- On-Line -- Up 05:20:44 -- 442536 Kbytes

SMX session statistics:
SMX control block: 0x45b22d28

Peer        SMX session        client        reads        writes
name        address            type
ol_rdemodb     46a90050         RSS Send         2715         2606

7.5 The sysmaster database

Alternatively, the sysmaster database can be used to retrieve this information.

syssmx

The syssmx table contains information about the SMX session. An SMX session is simply the handling of communications with the other servers connected in either RSS or SDS environments.

The following table shows the meaning of each column in the table.

Column Meaning
address The address in shared memory of the smx pipe for that connection
name The name of the connection
encryption_status Whether encryption is turned on or not
buffers_sent The number of buffers sent across the smx layer
buffers_recv The number of buffers received across the smx layer
bytes_sent The number of bytes sent across the smx layer
bytes_recv The number of bytes received across the smx layer
retries The number of retries for write calls
Example

Show a sample output query from the table:

Copy 
$ dbaccess sysmaster - -

Database selected.

> SELECT * FROM syssmx;

address            1169310504
name               ol_rdemodb
encryption_status  Disabled
buffers_sent       2880
buffers_recv       6409
bytes_sent         5219344
bytes_recv         182788
reads              6409
writes             2137
retries            443

1 row(s) retrieved.

>

7.6 Event alarms

The database administrator can also monitor the event alarms that are triggered for the RSS servers. When each event alarm is triggered, the Primary server writes a message to the message log that includes RSS server name. There are several situations when the Primary server triggers event alarms for RSS.

These are the most important alarms that need to be monitored:

  • RSS log replay position is falling too far behind the RSS source.

    This message displays when the log replay position for the RSS server is falling too far behind the Primary. If this trend continues, the Primary might not have a logical log file available when the RSS server requests it.

  • RSS server is not acknowledging log transmissions.

    If the Primary server does not get acknowledgement (ACK) back (after it reaches the limit of successful transmissions) due to a network issue, it will trigger this event alarm. The Primary server will not send any more logical log pages until an acknowledgement is received.

  • Error receiving a buffer from RSS server.

    The Primary server experienced an error receiving a message from the RSS server.

Info

The class ID used by these events is 40, and severity is ALRM_ATTENTION.

8 Exports in RSS servers

TO DO

This section is incomplete and will be concluded as soon as possible.