%SYSTEM.Mirror
abstract class %SYSTEM.Mirror extends %SYSTEM.Help
This class contains public mirroring methods which are accessable from any namespace. These methods can be invoked either via ##class(%SYSTEM.Mirror).(< methodname >) or via $SYSTEM.Mirror.(< methodname >). Most of the public API for mirroring is in the SYS.Mirror class however that class is only accessable to programs running in %SYS.Method Inventory
- GetMemberStatus()
- GetMemberType()
- GetMirrorNames()
- GetStatus()
- IsAsyncMember()
- IsBackup()
- IsMember()
- IsPrimary()
- MirrorName()
Methods
On failover members, and non-failover members which track only a single mirror, the MirrorName is optional. On instances which track more than one mirror, omitting the MirrorName (or passing "") returns summary information regarding the connection status (eg. m/n connected). Specifying the MirrorName returns the detailed information below regarding that mirror.
Return values are in $LIST format. The 1st item in the list is the current status of the member. In the future some status values may have additional pieces which carry more information.
The values for $LG(status,1) are:
- Not Initialized - This instance is not yet initialized, or not a member of the specified mirror.
- Primary - This instance is the primary mirror member. Like IsPrimary() this indicates that the node is active as the primary. $LG(status,2) contains 'Trouble' when the primary is in trouble state.
- Backup - This instance is connected to the primary as a backup member.
- Connected - This instance is an async member currently connected to the mirror.
- m/n Connected - Returned for async members which connect to more than one mirror when the MirrorName argument is omitted. <m> is the number of mirrors the instance is currently connected to, <n> is the number of mirrors the instance is configured to connect to.
- Transition - In a transitional state that will soon change when initialization or another operation completes. This status prompts processes querying a member's status to query again shortly. Failover members remain in this state while retrieving and applying journals when no other failover member is primary. This is an indication that it may become primary upon finishing, so a caller that is waiting for this member to become primary may wish to continue waiting; if there is another failover member that is primary, the state will be Synchronizing instead.
- Synchronizing - Starting up or reconnecting after being stopped or disconnected, retrieving and applying journal files in order to synchronize the database and journal state before becoming Backup or Connected.
- Waiting - For a failover member this means the member is unable to become the primary or backup for some reason. For an async member this has similar meaning, either there is some trouble preparing to contact the mirror or it failed to establish a connection to the mirror. In all cases a there should be a note in the console log as to the problem and the member should be retrying to detect when the trouble condition is resolved.
- Stopped - Mirroring is configured but not running and will not start automatically. Either the mirror management interface has been used to stop mirroring or the current state of the system has prevented mirroring from starting (examples include emergency startup mode, insufficient license, mirror service disabled, certain errors during mirroring initialization).
- Crashed - The mirror master job for this mirror is no longer running. Restarting InterSystems IRIS is required for mirroring to work again.
- Error - An unexpected error occured. Either an error was caught or the system is in some unexpected state. $LG(status,2) contains the value of the $ZERROR variable
- Down - This member is down. This is displayed by other members when this member is down.
The values returned are:
- Indeterminate - Startup is running and the configuration is not loaded yet
- Not Member - This instance is not configured to join a mirror
- Failover - This instance is configured as a failover member
- Async - This instance is configured as an async member but we cannot determine what kind of an async member it is. This occurs when a member reports its member type to another member or when the configuration cannot be read.
- Disaster Recovery - This instance is configured as a async member for disaster recovery purposes.
- Read-Only Reporting - This instance is configured as an async reporting node and the default for the local copy of the mirrored databases is that they are read-only.
- Read-Write Reporting - This instance is configured as an async reporting node and the default for the local copy of the mirrored databases is that they are writable.
Returns the names of the mirrors the instance is a member of in $LIST format, or NULL if the instance is not a mirror member.
GetStatus([MirrorName]) returns the current status of this mirror member.
On failover members, and non-failover members which track only a single
mirror, the MirrorName is optional. On instances which track more than one mirror,
omitting the MirrorName (or passing "") returns summary information regarding the connection
status. Specifying the MirrorName returns the detailed
information below regarding that mirror.
GetMemberStatus() returns the same information in a for more
suitable for displaying to a user. The form returned here may be more suitiable
for testing against in a program.
- NOTINIT - This instance is not yet initialized or not a member of the specified mirror.
- PRIMARY - This instance is the primary mirror member. Like IsMember() this indicates that the node is active as the primary.
- BACKUP - This instance is connected to the primary as a backup member.
- CONNECTED - This instance is an async member currently connected to its server.
- TRANSITION - In a transitional state that will soon change when initialization or another operation completes. This status prompts processes querying a member's status to query again shortly. Failover members remain in this state while retrieving and applying journals when no other failover member is primary. This is an indication that it may become primary upon finishing, so a caller that is waiting for this member to become primary may wish to continue waiting; if there is another failover member that is primary, the state will be SYNCHRONIZING instead. An instance may also enter the transition while stopping or restarting mirroring.
- SYNCHRONIZING - Starting up or reconnecting after being stopped or disconnected, retrieving and applying journal files in order to synchronize the database and journal state before becoming Backup or Connected.
- WAITING - For a failover member this means the member is unable to become the primary or backup for some reason. For an async member this has similar meaning, either there is some trouble preparing to contact the mirror or it failed to establish a connection to the mirror. In all cases a there should be a note in the console log as to the problem and the member should be retrying to detect when the trouble condition is resolved.
- STOPPED - Mirroring is configured but not running and will not start automatically. Either the mirror management interface has been used to stop mirroring or the current state of the system has prevented mirroring from starting (examples include emergency startup mode, insufficient license, mirror service disabled, certain errors during mirroring initialization).
- CRASHED - The mirror master job for this mirror is no longer running. Restarting InterSystems IRIS is required for mirroring to work again.
- MULTIASYNC^<m>/<n> - Returned for async members which connect to more than one mirror when the MirrorName argument is omitted. <m> is the number of mirrors the instance is currently connected to, <n> is the number of mirrors the instance is configured to connect to.
Test whether this system is connected to a primary as an async mirror member.
This reports true when this node has a data channel established to a primary
mirror member as an async member. The node can be configured as an async member
but this will report false if it does not have any data channels established at the time.
Return Value:
     
TRUE = node is currently connected to a mirror as an async member
     
FALSE = node is not currently connected to a mirror as an async member
Test whether this system is a backup mirror member.
A failover mirror member might report false for both IsPrimary and IsBackup
if it is in the process of connecting or has failed to connect for some
reason. IsBackup() is only true while the mirror data channel exists.
Return Value:
     
TRUE = node is currently connected to a mirror as a backup
     
FALSE = node is not currently connected to a mirror as a backup
Test whether this system is configured to join a mirror.
This method is useful when a site has code that should only be
run on the Primary node when the node is a mirror member. This
could be used in ^ZSTART or ^ZSTU to skip this code during startup
when the node is a mirror member (startup code for mirrors
should go in NotifyBecomePrimary^ZMIRROR).
This is also useful in conjunction with
$SYSTEM.Mirror.IsPrimary() in other code, such as
code that is run periodically via the TaskManager, to skip
running the code on non-primary mirror members as in
      quit:($SYSTEM.Mirror.IsMember() & '$SYSTEM.Mirror.IsPrimary())
Return Value:
     
0 - Node is not configured to join a mirror
     
1 - Node is configured as a failover mirror member
     
2 - Node is configured as an async mirror member
Test whether this system is the primary mirror member.
Return Value:
     
1 = node is the primary
     
0 = node is not the primary
Returns the name of the mirror if the instance is configured as a failover mirror member or NULL if it is not.