Upgrading a Mirror
This section provides instructions for upgrading InterSystems IRIS instances, an application, or both on the members of an InterSystems IRIS mirror.
As noted in the “Mirroring” chapter of the InterSystems IRIS High Availability Guide, all failover and DR async members of a mirror must be of the same InterSystems IRIS version, and can differ only for the duration of an upgrade. Once an upgraded member becomes primary, you cannot make use of the other failover member and any DR async members (and in particular cannot allow them to become the primary) until the upgrade is completed.
Mirroring does not require reporting async members to be of the same InterSystems IRIS version as the failover members, although application functionality may require it; for more information, see InterSystems IRIS Instance Compatibility in the “Mirroring” chapter of High Availability Guide.
There are four mirror upgrade paths to choose from. To determine which procedure you should follow, review the factors in the Choosing Mirror Upgrade Procedure section below. The four procedures are located in the Mirror Upgrade Procedures section below.
Also review the following two sections about upgrading a mirror:
Important:
On Linux systems supporting systemd, although it is possible to use either systemctl commands or the /etc/init.d/ISCAgent script to manage the ISCAgent, you must choose one method and use it exclusively; the ISCAgent should always be stopped using the method with which it was started. For more information, see Starting the ISCAgent on Linux Systems in the “Mirroring” chapter of the InterSystems High Availability Guide.
When you upgrade InterSystems IRIS on such a Linux system, a running ISCAgent is automatically restarted using systemd. If you are using the /etc/init.d/ISCAgent script to manage the ISCAgent, stop the agent before performing the upgrade so that it is not automatically restarted, then restart it using the script after the upgrade.
Choosing Mirror Upgrade Procedure
There are two primary factors to consider in choosing the procedure appropriate for your mirror upgrade:
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Are you upgrading to a maintenance release of the installed version of InterSystems IRIS, or to a new major version of InterSystems IRIS?
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Does the upgrade involve changes to mirrored databases?
Whenever you upgrade to a maintenance release and are not making any application upgrades, you do not have to consider the second question; you can always use the simple Maintenance Release Upgrade procedure, which renders the mirror unavailable only for the time it takes to execute a planned failover.
However, when you upgrade from one major InterSystems IRIS version to another, perform application upgrades, or both, there is the possibility that your upgrade involves changes to mirrored databases. Such changes must occur on the functioning primary failover member as part of the upgrade procedure, while application access is disabled. As a result, the upgrade requires more downtime than if you are not making any mirrored database changes. (The changes are then replicated by the mirror on the backup and any async members.)
Important:
Following a major upgrade, InterSystems recommends that you recompile all classes in all application namespaces on the instance and some routines must also be recompiled. Any application upgrade you perform may require changes to application data. In either of these situations, your upgrade may result in changes to mirrored databases.
If you are upgrading to a major release, are performing application upgrades, or both, you must determine whether any of the following conditions apply:
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Classes and routines are stored in mirrored databases that also contain application data. Classes must be recompiled on the primary (even if the application has not been upgraded). Recompiling routines on the primary is recommended.
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Data in mirrored databases must be upgraded due to an application upgrade; these changes must take place on the primary.
Note:
Since all Interoperability productions have mirrored application code, these conditions will always apply for mirrored environments with Interoperability productions.
If your major upgrade and/or application upgrade involves any of these conditions, use the Major Version Upgrade (Mirrored Database Changes) procedure, which renders the mirror unavailable only for the time it takes to execute a planned failover and make the required mirrored database changes.
If your upgrade does not involve any of the listed mirrored database changes, consider the Major Version Upgrade (No Mirrored Database Changes) procedure, which renders the mirror unavailable only for the time it takes to execute a planned failover.
If you have a significant planned maintenance window and minimizing mirror downtime is not a major concern, you may choose to use the simpler Major Version Upgrade with Planned Downtime procedure instead.
In the case of major upgrades, the general sequence of each procedure applies to upgrades of the mirror’s InterSystems IRIS instances, application code, or both; adapt individual steps depending on what you are upgrading.
Note:
Your circumstances may call for additional steps and details in a given procedure. If you are still unsure which procedure is appropriate for you, or whether a particular procedure is appropriate as stated, please contact the InterSystems Worldwide Response CenterOpens in a new tab (WRC).
Adding Mirror Members During an Upgrade
If you plan to add members to a mirror, you may want to defer this until you plan to perform one of the upgrades described in this section and add members of the new version during the upgrade, so that you do not have to upgrade them later. You can always add members of a newer version to a mirror during an upgrade, provided you immediately continue with and complete the upgrade as described, with one restriction: once a member of the newer version becomes primary, it must remain primary until all other members have been upgraded.
Adding new members during an upgrade can be very helpful when migrating a mirror to new hardware. Rather than upgrading one of the failover members before failing over to it, you can install a new instance of the new version on the target system, add it to the mirror as a DR async member, promote it to backup and then fail over to it, thus migrating the mirror primary to the new system. By repeating this technique you can then migrate the remaining failover member. The procedures in this section include steps for adding a new backup of the new version as an alternative to upgrading the existing backup, to illustrate this approach.
Mirror Upgrade Terms
In the procedures in this section, the following terms are used:
Upgrade classes and routines
Recompile all classes in all application namespaces on the instance. This should be done after an InterSystems IRIS major version upgrade (as described in Post-Upgrade Tasks) and/or application upgrade, which may involve one or more of the following operations, depending on your situation:
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As noted in the foregoing, when classes exist in any mirrored database that also contains application data, they must be recompiled locally on the functioning primary failover member (regardless of whether they are modified by an application upgrade). It is recommended that any existing routines are recompiled.
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Classes and routines stored in nonmirrored routines databases that are separate from application data can be recompiled on a mirror member regardless of whether it is the current primary.
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Classes and routines stored in separate nonmirrored routines database can also be “precompiled” by recompiling a copy of the database on a system that has already been upgraded to the target InterSystems IRIS release, then distributed to each mirror member following the upgrade.
System A
The mirror member that is initially the primary failover member.
System B
The mirror member that is initially the backup failover member.
System C
A newly-added DR async of the new InterSystems IRIS version that has been promoted to failover member.
Perform a graceful shutdown
Use the iris stop command to shut the instance down cleanly (see Controlling InterSystems IRIS Instances in the “Using Multiple Instances of InterSystems IRIS” chapter of the InterSystems IRIS System Administration Guide).
Viewing the Mirror Monitor
Use the Mirror Monitor page in the instance’s Management Portal to review the status of the mirror and its members; see Using the Mirror Monitor in the “Mirroring” chapter of the InterSystems IRIS High Availability Guide for more information.
Mirror Upgrade Procedures
There are four mirror upgrade paths to choose from. To determine which procedure you should follow, review the factors in the Choosing Mirror Upgrade Procedure section. The four procedures are:
The first three procedures are designed to let you perform the upgrade you need with the shortest possible application downtime; they differ to accommodate different upgrade circumstances. The last, which is a bit simpler, can be used for any type of upgrade when minimizing downtime is not a priority.
Maintenance Release Upgrade
If you are upgrading to an InterSystems IRIS maintenance release rather than a new major InterSystems IRIS version and are not making any application changes, use the following procedure, which renders the mirror unavailable only for the time required to execute a planned failover:
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To prevent failover from occurring until the backup is fully upgraded, set no failover.
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Perform one of the following two operations:
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Ensure that the backup (B or C) has become active by viewing the Mirror Monitor.
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Clear no failover.
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Perform a graceful shutdown of the primary (A). The mirror fails over and the backup (B or C) takes over as primary.
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Upgrade system A with the new version of InterSystems IRIS. System A becomes backup.
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If system C became primary and system B was demoted to DR async, upgrade system B.
Major Version Upgrade (Mirrored Database Changes)
If you are upgrading to a new major InterSystems IRIS version and/or performing an application upgrade and have determined that changes to mirrored databases are required (as described in Choosing a Mirror Upgrade Procedure), use the following procedure, which renders the mirror unavailable only for the time it takes to execute a planned failover and make the required mirrored database changes:
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To prevent failover from occurring until the backup is fully upgraded, set no failover.
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Perform one of the following two operations:
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Ensure that the backup (B or C) has become active by viewing the Mirror Monitor.
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Disallow new user access to the mirror using established practices at your site. Additionally, you must disable any application jobs that would normally start on system B when it becomes primary.
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Clear no failover.
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Perform a graceful shutdown of the primary (A). The mirror fails over and the backup (B or C) takes over as primary
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Upgrade mirrored classes and routines on the new primary (B or C). If an application upgrade requires further changes to mirrored databases, make these changes.
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Restore user access to the mirror.
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To prevent system A from taking over as primary until fully upgraded, set no failover
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Upgrade system A with the new version of InterSystems IRIS. System A becomes backup.
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Upgrade nonmirrored classes and routines on system A, if any.
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Clear no failover.
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If system C became primary and system B was demoted to DR async, upgrade system B and upgrade nonmirrored classes and routines on system B, if any.
Major Version Upgrade (No Mirrored Database Changes)
If you are upgrading to a new major InterSystems IRIS version and/or performing an application upgrade and have determined that changes to mirrored databases are not required (as described in Choosing a Mirror Upgrade Procedure), you may be able to use the following procedure.
This procedure is simplest for static applications where separate nonmirrored routines databases are always maintained. It can, however, be used even if the separate routines databases are normally mirrored by removing these databases from the mirror for the duration of the upgrade.
Important:
If the routines databases are normally mirrored, ensure that they do not contain any application data before removing them from the mirror.
This procedure cannot be used with normally mirrored routines databases if ECP application servers connect to the mirror.
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Enact a code freeze and application configuration freeze to disallow application changes during the upgrade, using established procedures at your site, to ensure that routines databases are not modified during the upgrade.
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To prevent failover from occurring until the backup is fully upgraded, set no failover.
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Perform one of the following two operations:
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Clear no failover.
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Perform a graceful shutdown of the primary (A). The mirror fails over and the backup (B or C) takes over as primary.
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To prevent system A from taking over as primary until fully upgraded, set no failover.
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Upgrade system A with the new version of InterSystems IRIS. System A becomes backup.
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Upgrade any nonmirrored classes and routines on system A.
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If system C became primary and system B was demoted to DR async, upgrade system B and upgrade nonmirrored classes and routines on system B, if any.
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For any mirrored routines databases that you removed from the mirror on backup (B or C) before it became the new primary, do the following:
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Remove the routines databases from the mirror on system A.
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Add the databases to the mirror on the new primary (B or C), then back them up and restore them on the backup (A) and DR async (B, if C is the primary), using the procedures for adding an existing database to a mirror provided in Adding Databases to a Mirror in the “Mirror” chapter of the InterSystems IRIS High Availability Guide. Retain these backups, as they represent the first backups of newly-added mirrored databases; older backups made prior to the upgrade cannot be used to restore these databases in the event of disaster.
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Clear no failover.
Major Version Upgrade with Planned Downtime
If you are upgrading to a new major InterSystems IRIS version and/or performing an application upgrade and have a significant planned maintenance window that obviates the need to minimize mirror downtime, you may prefer to use the following simpler procedure, regardless of whether changes to mirrored databases on the primary are required:
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Disallow all user access to the mirror using established practices at your site. Additionally, you must disable any application jobs that would normally start on instance startup.
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Perform a graceful shutdown of the backup (B).
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Perform a graceful shutdown of the primary (A).
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Upgrade system A with the new version of InterSystems IRIS. System A becomes primary.
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Upgrade mirrored classes and routines on system A. If an application upgrade requires further changes to mirrored databases, make these changes.
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Upgrade nonmirrored classes and routines on system A, if any.
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Perform one of the following two operations:
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If system C became primary and system B was demoted to DR async, upgrade system B and upgrade nonmirrored classes and routines on system B, if any.
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Restore user access to the mirror.
