Hi! As part of READ COMMITTED READ CONSISTENCY, it was added context variables (under RDB$GET_CONTEXT's SYSTEM namespace) GLOBAL_CN and SNAPSHOT_CN.
GLOBAL_CN: Most current value of global Commit Number counter SNAPSHOT_CN: Value of Commit Number of currently database snapshot: either transaction level (for SNAPSHOT or CONSISTENCY transaction), or request level (for READ COMMITTED READ CONSISTENCY transaction). NULL, if snapshot is not exist. It was also added function RDB$GET_TRANSACTION_CN( <transaction number> ): Returns commit number of given transaction. I may be wrong but as RDB$GET_TRANSACTION_CN does not get the SNAPSHOT_CN of active transactions, but only commit number of committed transactions, these set of (user exposed) feature is now currently only for curiosity or debug purposes, but not for monitoring. If SNAPSHOT_CN is exposed outside own transaction/attachment (say in MON$ or with another function as RDB$GET_TRANSACTION_CN that gets the SNAPSHOT_CN from another transaction) that feature may also be used for monitoring. I think that must be considered. Despite that, with this thread feature SNAPSHOT_CN gains a function, i.e., to start more than one transaction (could be in different attachments) seeing the same initial data. It's agreed that we also need a transaction info code to get the same thing currently returned by SNAPSHOT_CN of SNAPSHOT transactions. So all this functionality is very related, so they names must match accordingly. Vlad is proposing the new info code to be named fb_info_tra_snapshot_number. I have no problem with it, provided that SNAPSHOT_CN is also renamed (with he seems to be open), but for what? SNAPSHOT_NUMBER too? (I have no problem with that) So if we consistently call that number a "SNAPSHOT NUMBER" the path to name the new TPB and SET TRANSACTION subclause becomes easy. Which then I would go to isc_tpb_at_snapshot_number and SET TRANSACTION SNAPSHOT [ AT NUMBER <n> ]. Adriano Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
