The purge command to the thl command deletes sequence number information from the THL files.
thl purge
[-low # ] | [-high # ]
[-y ] [-no-checksum ]
The purge command deletes the THL data according to the following rules:
Purging all data requires that the THL information either be recreated from the source table, or reloaded from the Primary replicator.
Without any specification, a purge command will delete all of the stored THL information.
When only -high is specified,
delete all the THL data up to and including the specified sequence
number.
When only -low is specified,
delete all the THL data from and including the specified sequence
number.
With a range specification, using one or both of the
-low and
-high options, the range of
sequences will be purged. The rules are the same as for the
list command, enabling
purge from the start to a sequence, from a sequence to the end, or all
the sequences within a given range. The ranges must be on the boundary
of one or more log files. It is not possible to delete THL data from
the middle of a given file.
For example, consider the following list of THL files provided by thl index:
shell> thl index
LogIndexEntry thl.data.0000000377(5802:5821)
LogIndexEntry thl.data.0000000378(5822:5841)
LogIndexEntry thl.data.0000000379(5842:5861)
LogIndexEntry thl.data.0000000380(5862:5881)
LogIndexEntry thl.data.0000000381(5882:5901)
LogIndexEntry thl.data.0000000382(5902:5921)
LogIndexEntry thl.data.0000000383(5922:5941)
LogIndexEntry thl.data.0000000384(5942:5961)
LogIndexEntry thl.data.0000000385(5962:5981)
LogIndexEntry thl.data.0000000386(5982:6001)
LogIndexEntry thl.data.0000000387(6002:6021)
LogIndexEntry thl.data.0000000388(6022:6041)
LogIndexEntry thl.data.0000000389(6042:6061)
LogIndexEntry thl.data.0000000390(6062:6081)
LogIndexEntry thl.data.0000000391(6082:6101)
LogIndexEntry thl.data.0000000392(6102:6121)
LogIndexEntry thl.data.0000000393(6122:6141)
LogIndexEntry thl.data.0000000394(6142:6161)
LogIndexEntry thl.data.0000000395(6162:6181)
LogIndexEntry thl.data.0000000396(6182:6201)
LogIndexEntry thl.data.0000000397(6202:6221)
LogIndexEntry thl.data.0000000398(6222:6241)
LogIndexEntry thl.data.0000000399(6242:6261)
LogIndexEntry thl.data.0000000400(6262:6266)The above shows a range of THL sequences from 5802 to 6266.
To delete all of the THL from the start of the list, sequence no 5802, to
6021 (inclusive), use the -high to
specify the highest number to be removed (6021):
shell> thl purge -high 6021
WARNING: The purge command will break replication if you delete all
events or delete events that have not reached all slaves.
Are you sure you wish to delete these events [y/N]?
y
Deleting events where SEQ# <=6021
2020-02-10 16:31:36,235 [ - main] INFO thl.THLManagerCtrl Transactions deletedRunning a thl index, sequence numbers from 6022 to 6266 are still available:
shell> thl index
LogIndexEntry thl.data.0000000388(6022:6041)
LogIndexEntry thl.data.0000000389(6042:6061)
LogIndexEntry thl.data.0000000390(6062:6081)
LogIndexEntry thl.data.0000000391(6082:6101)
LogIndexEntry thl.data.0000000392(6102:6121)
LogIndexEntry thl.data.0000000393(6122:6141)
LogIndexEntry thl.data.0000000394(6142:6161)
LogIndexEntry thl.data.0000000395(6162:6181)
LogIndexEntry thl.data.0000000396(6182:6201)
LogIndexEntry thl.data.0000000397(6202:6221)
LogIndexEntry thl.data.0000000398(6222:6241)
LogIndexEntry thl.data.0000000399(6242:6261)
LogIndexEntry thl.data.0000000400(6262:6266)
To delete the last two THL files, specify the sequence number at the start
of the file, 6242 to the -low to
specify the sequence number:
shell> thl purge -low 6242 -y WARNING: The purge command will break replication if you delete all events or delete events that have not reached all slaves. Deleting events where SEQ# >= 6242 2020-02-10 16:40:42,463 [ - main] INFO thl.THLManagerCtrl Transactions deleted
A thl index shows the sequence as removed:
shell> thl index
LogIndexEntry thl.data.0000000388(6022:6041)
LogIndexEntry thl.data.0000000389(6042:6061)
LogIndexEntry thl.data.0000000390(6062:6081)
LogIndexEntry thl.data.0000000391(6082:6101)
LogIndexEntry thl.data.0000000392(6102:6121)
LogIndexEntry thl.data.0000000393(6122:6141)
LogIndexEntry thl.data.0000000394(6142:6161)
LogIndexEntry thl.data.0000000395(6162:6181)
LogIndexEntry thl.data.0000000396(6182:6201)
LogIndexEntry thl.data.0000000397(6202:6221)
LogIndexEntry thl.data.0000000398(6222:6241)
The confirmation message can be bypassed by using the
-y option, which implies
that the operation should proceed without further confirmation.
The optional argument -no-checksum
ignores the checksum information on events in the event that the checksum
is corrupt.
When purging, the THL files must be writeable; the replicator must either be offline or stopped when the purge operation is completed.
A purge operation may fail for the following reasons:
Fatal error: The disk log is not writable and cannot be purged.
The replicator is currently running and not in the
OFFLINE state. Use
trepctl offline to release the write lock n the THL
files.
Fatal error: Deletion range invalid; must include one or both log end points: low seqno=0 high seqno=1000
An invalid sequence number or range was provided. The purge operation will refuse to purge events that do not exist in the THL files and do not match a valid file boundary, i.e. the low figure must match the start of one file and the high the end of a file. Use thl index to determine the valid ranges.